Head-to-head comparison across 5benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Claude Sonnet 4.5
67
GPT-5.5
89
Verified leaderboard positions: Claude Sonnet 4.5 unranked · GPT-5.5 #2
Pick GPT-5.5 if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if mathematics is the priority or you want the cheaper token bill.
Agentic
+26.5 difference
Coding
+18.6 difference
Reasoning
+71.4 difference
Knowledge
+17.0 difference
Math
+35.3 difference
Claude Sonnet 4.5
GPT-5.5
$3 / $15
$5 / $30
N/A
N/A
N/A
N/A
200K
1M
Pick GPT-5.5 if you want the stronger benchmark profile. Claude Sonnet 4.5 only becomes the better choice if mathematics is the priority or you want the cheaper token bill.
GPT-5.5 is clearly ahead on the provisional aggregate, 89 to 67. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5's sharpest advantage is in reasoning, where it averages 85 against 13.6. The single biggest benchmark swing on the page is ARC-AGI-2, 13.6% to 85%. Claude Sonnet 4.5 does hit back in mathematics, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $3.00 input / $15.00 output per 1M tokens for Claude Sonnet 4.5. That is roughly 2.0x on output cost alone. GPT-5.5 is the reasoning model in the pair, while Claude Sonnet 4.5 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5.5 gives you the larger context window at 1M, compared with 200K for Claude Sonnet 4.5.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 89 to 67. The biggest single separator in this matchup is ARC-AGI-2, where the scores are 13.6% and 85%.
Claude Sonnet 4.5 has the edge for knowledge tasks in this comparison, averaging 83.4 versus 66.4. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Claude Sonnet 4.5 has the edge for coding in this comparison, averaging 77.2 versus 58.6. GPT-5.5 stays close enough that the answer can still flip depending on your workload.
Claude Sonnet 4.5 has the edge for math in this comparison, averaging 87 versus 51.7. GPT-5.5 stays close enough that the answer can still flip depending on your workload.
GPT-5.5 has the edge for reasoning in this comparison, averaging 85 versus 13.6. Inside this category, ARC-AGI-2 is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for agentic tasks in this comparison, averaging 81.8 versus 55.3. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
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