Head-to-head comparison across 3benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.5 Pro
100
Kimi K2.5 (Reasoning)
78
Pick GPT-5.5 Pro if you want the stronger benchmark profile. Kimi K2.5 (Reasoning) only becomes the better choice if mathematics is the priority or you want the cheaper token bill.
Agentic
+35.5 difference
Knowledge
+30.1 difference
Math
+43.7 difference
GPT-5.5 Pro
Kimi K2.5 (Reasoning)
$30 / $180
$0.6 / $3
N/A
N/A
N/A
N/A
1M
128K
Pick GPT-5.5 Pro if you want the stronger benchmark profile. Kimi K2.5 (Reasoning) only becomes the better choice if mathematics is the priority or you want the cheaper token bill.
GPT-5.5 Pro is clearly ahead on the provisional aggregate, 100 to 78. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.5 Pro's sharpest advantage is in agentic, where it averages 90.1 against 54.6. The single biggest benchmark swing on the page is BrowseComp, 90.1% to 60.6%. Kimi K2.5 (Reasoning) does hit back in mathematics, so the answer changes if that is the part of the workload you care about most.
GPT-5.5 Pro is also the more expensive model on tokens at $30.00 input / $180.00 output per 1M tokens, versus $0.60 input / $3.00 output per 1M tokens for Kimi K2.5 (Reasoning). That is roughly 60.0x on output cost alone. GPT-5.5 Pro gives you the larger context window at 1M, compared with 128K for Kimi K2.5 (Reasoning).
GPT-5.5 Pro is ahead on BenchLM's provisional leaderboard, 100 to 78. The biggest single separator in this matchup is BrowseComp, where the scores are 90.1% and 60.6%.
Kimi K2.5 (Reasoning) has the edge for knowledge tasks in this comparison, averaging 87.3 versus 57.2. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
Kimi K2.5 (Reasoning) has the edge for math in this comparison, averaging 96.1 versus 52.4. GPT-5.5 Pro stays close enough that the answer can still flip depending on your workload.
GPT-5.5 Pro has the edge for agentic tasks in this comparison, averaging 90.1 versus 54.6. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
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