ChatGPT: cites current crawlable content, strong recency bias. Perplexity: 5-10 citations per answer, most accessible — needs fast-loading structured pages. Claude: more conservative, trained data coverage matters more than current web — build third-party mentions. Gemini: Google knowledge graph integration — optimize Google Business Profile and structured data. Run the Omni AI Visibility Engine to check all four simultaneously and build a visibility matrix by model and query type. System at omnionlinestrategies.com/ai-discoverability-demo.