Verdict
GPT-5.5 Pro leads 6–4 across 10 shared benchmarks.
Gemini 3.1 Pro 4 · GPT-5.5 Pro 6 · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Reasoning: Gemini 3.1 Pro leads 4–0 across 4 shared reasoning benchmarks (largest gap: SimpleQA Verified, 77.3 vs 64.5 — 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.
Agentic / Tool Use
“Gemini 3.1 Pro was evaluated across a range of benchmarks, including reasoning, multimodal capabilities, agentic tool use, multi-lingual performance, and long-context.”
Multimodal
“a suite of highly capable, natively multimodal reasoning models”
Reasoning
“Gemini 3.1 Pro is Google's most advanced model for complex tasks.”
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 6–4 across 10 shared benchmarks. Gemini 3.1 Pro leads 4 benchmarks and GPT-5.5 Pro leads 6. Higher isn't always better — see the integrity caveats on each benchmark.
Gemini 3.1 Pro 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.
Gemini 3.1 Pro leads reasoning 4–0. GPT-5.5 Pro leads math 2–0.