Verdict
GPT-5.5 Pro leads 10–0 across 10 shared benchmarks.
Gemini 3.5 Flash 0 · GPT-5.5 Pro 10 · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Reasoning: GPT-5.5 Pro leads 3–0 across 3 shared reasoning benchmarks (largest gap: ARC-AGI, 96.5 vs 92.5 — single evaluator).
Math: GPT-5.5 Pro leads 2–0 across 2 shared math benchmarks (largest gap: FrontierMath-Tier-4-v2-Private, 78.05 vs 26.83 — single evaluator).
Vendor claims — compare against the measured scores above. A claim is what a developer says about its own model, not an independent measurement.
No vendor claims on file for Gemini 3.5 Flash.
General
“In GPT-5.5 Pro, early testers are seeing a significant step up in both the difficulty and quality of work ChatGPT can take on”
Reasoning
“GPT-5.5 Pro, designed for even harder questions and higher-accuracy work, is available to Pro, Business, and Enterprise users.”
Writing
“testers found GPT-5.5 Pro's responses significantly more comprehensive, well-structured, accurate, relevant, and useful”
GPT-5.5 Pro leads 10–0 across 10 shared benchmarks. Gemini 3.5 Flash leads 0 benchmarks and GPT-5.5 Pro leads 10. Higher isn't always better — see the integrity caveats on each benchmark.
Gemini 3.5 Flash and GPT-5.5 Pro have 10 benchmarks in common in our data — those are the only rows where a direct, apples-to-apples comparison is drawn.
GPT-5.5 Pro leads reasoning 3–0. GPT-5.5 Pro leads math 2–0.