Sill vs Profound: AI Visibility Monitoring and Experimentation Compared

Profound ($99-$5K+/mo) is the highest-funded company in the AI visibility space, with $155M raised across rounds led by Lightspeed, Sequoia, and Kleiner Perkins. Their platform tracks brand visibility across AI engines, provides citation analysis, and connects visibility data to behavioral analytics and conversion attribution. The standout feature is Prompt Volumes: real AI search demand data showing how often specific queries are asked across AI platforms. This is proprietary panel data from hundreds of millions of prompts, and no other company in the market has replicated it. Profound serves 700+ enterprise customers, including 10% of the Fortune 500, and was named a G2 Winter 2026 Leader with 140+ reviews.

Sill (Free-$225/mo) is building the experimentation layer for GEO: the ability to measure whether a specific content change caused an observed AI visibility shift, rather than simply observing that visibility changed. All 6 AI platforms (ChatGPT, Perplexity, Gemini, Google AI Overviews, Claude, Grok) are included at every pricing tier, including the free plan. Sill also provides GEO recommendations (748 generated across 62 brands, 87% on-site), Brand Watchdog for factual accuracy monitoring, and daily SOV tracking.

The core difference: Profound tells you what is happening across AI engines with the deepest dataset available. Sill is building the infrastructure to tell you whether what you did caused what happened. These are sequential problems. Most teams need observation first, experimentation second. The question is which problem you are solving today and what your budget allows.

Prompt Volumes is Profound's most defensible feature. It shows how often specific queries are asked across AI platforms, giving teams actual demand data for AI search. Traditional SEO has Google Search Console and keyword volume tools; AI search had nothing comparable until Profound built this. The data comes from a proprietary panel of hundreds of millions of prompts and is available from the Growth tier ($399/mo) upward. For content strategy, knowing which AI queries have volume is the equivalent of knowing which keywords to target in traditional search.

Actions generates content briefs based on competitive gaps identified in the visibility data. Rather than telling teams "your SOV dropped," it suggests specific content to create or update. This is available from the Growth tier and represents Profound's move from monitoring into prescriptive guidance.

Behavioral analytics and conversion attribution connect AI visibility to downstream business impact through a partnership with Partnerize. This is the closest the monitoring tier gets to answering the attribution question: did AI visibility drive revenue? Enterprise teams with the budget for both the visibility platform and the attribution integration can connect these signals in a way no other monitoring tool offers.

Platform coverage at enterprise tier includes 10+ AI engines. Profound's Starter plan ($99/mo) covers ChatGPT only; Growth ($399/mo) adds Perplexity and Google AI Overviews; full coverage across Claude, Grok, Meta AI, DeepSeek, and other engines requires enterprise pricing starting at approximately $2,000-$5,000+/mo. The dataset at enterprise tier is the most comprehensive in the market.

Profound Actions is Profound's content workflow feature. It scans cited sources for competitors, identifies gaps in a brand's own coverage, and generates briefs the content team can take to production. The output is a prioritized backlog of pages to write with topic clusters and suggested angles.

Sill Recommendations covers different ground: instead of generating briefs, Sill maps each recommendation to one of 47 evidence-ranked GEO tactics with a measured effect size, paces work to the team's shipping capacity, and when a recommendation is marked done, auto-routes the change to the experimentation engine to measure whether it moved SOV. Actions is upstream (what to write); Recommendations is end-to-end (what to do, when to do it, whether it worked). Sill generated 748 recommendations across 62 brands with 87% on-site fixes; the experimentation loop converts recommendation completion into a per-platform lift estimate with statistical controls. See introducing Recommendations for the full workflow.

Full platform coverage from day one. Sill includes ChatGPT, Perplexity, Gemini, Google AI Overviews, Claude, and Grok at every pricing tier. The free plan (5 prompts) covers all 6 platforms. The $90/mo Basic plan (120 prompts) covers all 6 platforms. There are no per-platform add-on fees. This matters because 55% of brands show a 10+ point SOV spread across AI engines; monitoring one platform and missing five others leaves a significant visibility gap. Profound's $99/mo Starter covers ChatGPT only; comparable multi-platform coverage requires enterprise pricing.

GEO experimentation with statistical controls. As covered in our hub comparison of GEO testing tools, Sill is building the experimentation layer that separates "SOV moved" from "our change caused SOV to move." The system uses unaffected prompts as controls, fits per-platform models rather than averaging across engines, and applies calibration to establish empirical false positive rates. This is the capability gap that no monitoring platform addresses today, including Profound. The first experiment takes 6-8 weeks; subsequent experiments take 2-4 weeks.

GEO recommendations. Sill has generated 748 GEO recommendations across 62 brands, with 87% being on-site fixes. These are actionable implementation steps grounded in a 47-tactic codex ranked by evidence strength from peer-reviewed research.

Brand Watchdog. Automated monitoring of factual claims AI platforms make about your brand, compared against a verified fact profile. When an AI engine states something incorrect about your company (pricing, features, founding date, leadership), Watchdog flags the discrepancy. This is a different class of monitoring than SOV tracking: it watches for factual accuracy, not just visibility.

Pricing reflects publicly available information as of April 2026. Profound's enterprise pricing is estimated based on published tier structure and industry reporting.

Choose Profound if you are an enterprise team with a $2,000+/mo budget and need the deepest AI visibility dataset available. Prompt Volumes is genuinely unique and provides strategic value for content planning that no other tool replicates. If your team needs revenue attribution connected to AI visibility, Profound's Partnerize integration is the only option in the market. If you require SOC 2 Type II compliance or SSO today, Profound has it and Sill does not yet.

Choose Sill if you want to start monitoring across all 6 major AI platforms without committing budget upfront. Sill's free tier provides what Profound's $99/mo Starter plan does not: multi-platform coverage. If your team needs to measure whether content changes actually caused visibility shifts (rather than observing that shifts happened), Sill's experimentation engine is the only option in the market with statistical controls for GEO. If you are mid-market ($1M-$50M revenue) and cannot justify $5,000+/mo for meaningful multi-platform coverage, Sill's pricing structure was designed for your budget.

These tools are not direct substitutes. Profound has the most data; Sill has the experimentation methodology. A team with the budget for both could reasonably use Profound for monitoring and demand intelligence alongside Sill for experimentation. For most teams, the decision comes down to budget and whether the priority today is observation or measurement. For the full landscape of GEO testing and experimentation tools, see our comprehensive comparison.