Verdict
GPT-5.5 Pro leads 8–1 across 9 shared benchmarks.
GPT-5.4 Pro 1 · GPT-5.5 Pro 8 · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Reasoning: GPT-5.5 Pro leads 3–1 across 4 shared reasoning benchmarks (largest gap: SimpleQA Verified, 64.5 vs 47.8 — 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 GPT-5.4 Pro.
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 8–1 across 9 shared benchmarks. GPT-5.4 Pro leads 1 benchmark and GPT-5.5 Pro leads 8. Higher isn't always better — see the integrity caveats on each benchmark.
GPT-5.4 Pro and GPT-5.5 Pro have 9 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 3–1.