Two years ago the question was simple. You hired an SEO agency, you measured rankings and organic traffic, and you renewed the contract if the numbers were good. Today the same conversation has three options on the table. A specialist SEO agency that knows traditional search inside out. A specialist AEO agency focused entirely on getting your brand cited in ChatGPT, Perplexity, Claude, Gemini, and Google AI Overviews. Or a combined agency that does both as one program. The harder question that follows is how you actually tell which one is producing returns, because the old measurement playbook does not capture what AI driven search is doing to your pipeline.
This guide breaks down each option, who it fits, what to look for in a partner, and exactly how to measure whether the work is generating real ROI rather than vanity metrics.
Why This Is Even a Question Now
For most of the last decade, search marketing meant Google. Optimizing for Google was a complete strategy because Google was where the buying journey started. That assumption no longer holds. A growing share of high intent research now starts in an AI assistant, and in many categories the answer that assistant gives can determine which brands make the shortlist before the buyer ever runs a search query.
The exact numbers vary by industry, but the direction is consistent. Categories with informed, considered buyers like B2B software, financial services, healthcare, home improvement, and professional services are seeing the largest shift. Even in categories where Google still dominates discovery, AI overviews are reshaping click behavior on the queries that do happen there.
The result is that the work of earning visibility now spans two related but distinct disciplines, and the right agency choice depends on where your buyers actually are and where your own team has and does not have coverage today.
Option 1: A Specialist SEO Agency
A specialist SEO agency is what most companies already know. The work focuses on technical SEO, on page optimization, content production for ranking, link earning, and reporting on rankings and organic traffic. The discipline is mature, the playbooks are well established, and the talent market is deep.
When this fits. You are in a category where traditional Google search still drives the majority of buyer behavior, you have a large existing site that needs technical and content optimization, your competitors are still investing heavily in SEO, and your buying audience tends to skew toward search habits rather than AI assistant habits. Local services businesses, ecommerce in commodity categories, and many consumer brands still fit this profile.
What to look for. Real technical depth, not just content production. Case studies in your category or close to it. A clear methodology for keyword prioritization. Honest discussion of timelines, because anyone promising fast SEO results is either inexperienced or selling you something risky. Tooling and reporting that goes beyond rankings to revenue and pipeline.
The risk. A pure SEO agency may underweight or ignore the AI channel entirely, which means you are flying blind on the part of the buyer journey that is shifting fastest. If the agency cannot answer how your brand appears in ChatGPT or Perplexity for your most important queries, that is a meaningful gap.
Option 2: A Specialist AEO Agency
A specialist AEO agency focuses entirely on earning visibility inside AI answer engines. The work includes auditing how your brand currently appears across ChatGPT, Claude, Perplexity, Gemini, Google AI Overviews, and emerging tools. Optimizing content for the way AI engines parse and cite information. Earning third party citations in the sources LLMs treat as trusted. Implementing structured data and schema for AI extraction. Monitoring citation share, mention frequency, and sentiment over time.
When this fits. Your buyers are clearly using AI assistants for the kind of research your category is sold into, you have already built a credible SEO foundation that does not need much new investment, your internal team is already strong on traditional search, or you want to move fast on AEO specifically and bring an SEO agency in separately.
What to look for. A real measurement stack for AEO, including tooling that tracks citations across the major answer engines over time. A clear point of view on which queries matter for your category. Production capacity for the kind of answer led content AI engines reward. Experience with third party citation work, not just on site optimization. Honest framing of AEO as a fast moving channel that requires continuous attention.
The risk. Pure AEO without SEO leaves a foundation gap, because the same signals that help AEO also help SEO and you are paying for only half the value. Also, the AEO agency market is very young, and a real specialist is different from a generalist who added AEO to the pitch deck last quarter.
Option 3: A Combined Agency That Does Both
A combined agency runs SEO and AEO as a single program. The team understands that the same content asset can be designed to rank in Google and to be cited in ChatGPT, that the same third party citation can lift both channels, and that the same schema can serve both purposes. Reporting is unified, so leadership sees one picture of search visibility rather than two disconnected dashboards.
When this fits. Many organizations, especially those without strong in house coverage of both channels. The combined model tends to be more efficient because it avoids duplicate work, more strategic because the channels inform each other, and easier to manage because there is one accountable partner rather than two competing for credit. It also makes the measurement question easier, because the agency is responsible for the full picture rather than only the half they own.
What to look for. Genuine depth in both disciplines, not a strong SEO team with AEO bolted on. Integrated reporting that shows how the two channels contribute to a shared pipeline number. A point of view on how the work is sequenced, because AEO produces faster early signals and SEO produces durable compounding. References from clients who can speak to results in both channels.
The risk. A surface level combined offering that is actually two separate teams that do not coordinate. The integration has to be real, or you are paying for a combined agency and getting two siloed ones.
How to Choose Between the Three
A few questions usually clarify the right path.
Where are your buyers researching today. If your sales team can already give you anecdotes about prospects mentioning ChatGPT or Perplexity, AEO needs to be in the program. If your customers are still finding you primarily through Google and word of mouth, SEO weight should be higher in the mix, but AEO still belongs because the trend is one directional.
What does your internal team already cover well. If you have a strong in house SEO function and just need help on the AI side, a specialist AEO agency is reasonable. If you have neither, a combined agency saves you from coordinating two vendors.
How quickly do you need to see results. AEO produces visible early movement in weeks. SEO produces durable results over quarters. If leadership pressure requires near term proof of life, weight the program toward the channel that can deliver it while the longer play matures.
How mature is your measurement. If you do not have a clear picture of attribution today, the combined model is usually easier because one partner is accountable for the full funnel impact rather than splitting credit across two.
How to Tell Which One Is Generating ROI
This is the question most companies struggle to answer well, and it is also the question that protects you from paying for activity that does not produce results.
The SEO ROI Picture
For traditional SEO, the chain from work to revenue is well understood, even if attribution remains imperfect.
Leading indicators include indexed pages, keyword coverage, average position on tracked terms, impressions in Search Console, and organic click through rate. These should move within the first quarter of meaningful work.
Mid funnel indicators include organic sessions, organic engaged sessions, assisted conversions, and branded versus non branded traffic mix. These should move in the second and third quarter.
Bottom line indicators include organic pipeline created, organic closed revenue, customer acquisition cost from organic, and ratio of organic to paid pipeline. In most engagements we see, a working SEO program produces a measurable shift in these numbers within two to four quarters, though the exact timing varies with starting authority and category competitiveness.
The honest test for SEO ROI is to compare the trend on these numbers in the months after the agency started with the trend in the months before, controlling for any obvious confounds like a site migration, a major product launch, or a paid channel change.
The AEO ROI Picture
AEO measurement is newer and the tooling is evolving, but the picture is becoming clearer.
Leading indicators include citation share on a defined set of priority queries across the major answer engines, mention frequency, and sentiment of those mentions. A real AEO program should be able to show a baseline, a current state, and the trajectory between them on a weekly cadence.
Mid funnel indicators include branded search volume, direct traffic from likely AI referrals, and qualified inbound mentions where the prospect references finding you through an AI tool. Branded search lift is one of the strongest practical signals because it captures the people who heard your name from an AI and then went to look you up.
Bottom line indicators include pipeline that originated from AI driven discovery, even when the attribution touch shows direct or branded search rather than the AI itself. The agency should be working with your revenue team to instrument simple capture in your CRM, such as a "how did you hear about us" field with an AI tools option and a sales team trained to ask the question on first calls.
The honest test for AEO ROI is the combination of citation share trend, branded search lift, and self reported AI driven inbound. If all three are moving in the right direction, the program is producing value even when traditional attribution tools cannot fully see it.
Combined ROI
When a single agency is responsible for both channels, the cleanest measurement is unified pipeline and revenue from all organic discovery, with the agency reporting the underlying contribution from each channel and how they interact. The interaction matters because a brand cited in ChatGPT often produces a branded search that hits a strong SEO page, and the resulting pipeline is the product of both channels working together.
Demand that your agency report the full picture, not just the half that is easiest to measure. If the team can only show rankings or only show citations, you do not yet have a real picture of ROI.
Red Flags in Any Pitch
A few warning signs reliably predict an engagement that will not deliver.
Guarantees of specific results in a specific timeframe. No reputable partner promises a first page Google ranking by a specific date or a specific citation share in ChatGPT, because neither outcome is fully in their control.
Reporting that focuses on activity rather than outcome. If the monthly report is mostly a list of pages published and links built, with no clear connection to pipeline, you are paying for motion rather than results.
A team that cannot articulate how SEO and AEO interact. If the agency treats them as completely separate disciplines with no shared playbook, you will end up paying for duplicate work and missing the compounding effects.
No baseline measurement at the start. Any serious engagement starts with a documented baseline so that progress is provable. If the agency cannot show you a current state report in the first month, the future ROI report will not be credible either.
No clear definition of success agreed up front. The conversation about whether the work is delivering should be much easier if you and the agency wrote down what success looks like before the work started.
Questions to Ask Every Agency in the Sales Process
These questions separate real partners from polished sales pitches.
How will you measure AEO specifically, and what tooling do you use to track citation share over time across the major answer engines.
Show me a recent client report that includes both SEO and AEO results in one view.
How do you sequence the work so we see early proof of progress while the longer SEO play matures.
Who on your team is accountable for our outcome and what is their direct experience with companies that look like ours.
What does the first 90 days actually look like, with specific deliverables in each two week increment.
How do you adjust the plan if the early data shows the original strategy is not working.
What will you need from us to make this work, and what happens if we cannot provide it.
Why Most Companies Are Best Served By a Combined Partner
For many companies, a combined SEO and AEO agency is the right answer for three practical reasons.
The work overlaps. The same content investment, the same schema work, and the same third party citation effort serves both channels. Splitting that work across two agencies creates duplication and friction.
The buyer journey now crosses both channels. A prospect may discover you in ChatGPT, then run a branded search on Google, then land on a comparison page that needs to rank well, then revisit an AI assistant for a final shortlist check. One partner who owns the full journey is in a much better position to optimize the chain than two partners who own halves of it.
The measurement is cleaner. When one agency is accountable for unified pipeline contribution, the ROI conversation is one conversation rather than a finger pointing exercise between two vendors.
At Proven ROI we run both as a single program because it is what produces the best client outcomes. We started with traditional SEO years ago, expanded into AEO as soon as the channel became material, and built the measurement stack to report both as a unified pipeline number. Our clients see early movement on AEO inside the first quarter while the SEO foundation compounds underneath it, and the reporting answers the ROI question on every monthly call rather than once a year.
The Bottom Line
You have three real options. A specialist SEO agency if your buyers are still primarily on Google and your priority is durable traditional search visibility. A specialist AEO agency if your SEO is already strong and your priority is fast progress on AI driven discovery. A combined agency if you want one accountable partner for the full picture, which fits many of the companies we see in the market today.
The ROI question is answerable in all three cases if you set up the measurement correctly. Define the baseline, agree on the leading, mid funnel, and bottom line metrics that matter, and demand reporting that connects activity to pipeline. The right partner welcomes the scrutiny because the work holds up.
If you want help thinking through which of these three paths fits your business, we are happy to talk it through. The best engagement starts with a clear picture of where you are and where the value is, not a pitch deck.