Vanaxity insights tagged AI model selection - notes on AI content, SEO, GEO and AEO from Van Data Team.
Anthropic released Claude Opus 5.5 on September 22, 2026 and Claude Sonnet 5.5 on September 28. Sonnet 5.5 costs half as much per token and runs faster. On independent Artificial Analysis tests at top settings, the two are nearly tied on documents, spreadsheets and automation, but Opus 5.5 is far more reliable on facts and costs less per task. At matched lower settings, Opus 5.5 wins every test for a little more money, while Sonnet 5.5 starts answering much sooner. For marketing teams, the right choice depends on the task: accuracy-critical content favors Opus, and fast, high-volume drafting favors Sonnet.
