Head-to-head comparison across 5benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.5
89
Kimi K2.5 (Reasoning)
78
Verified leaderboard positions: GPT-5.5 #2 · Kimi K2.5 (Reasoning) unranked
Pick GPT-5.5 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
+27.2 difference
Coding
+18.2 difference
Knowledge
+20.9 difference
Math
+44.4 difference
Multimodal
+9.5 difference
GPT-5.5
Kimi K2.5 (Reasoning)
$5 / $30
$0.6 / $3
N/A
N/A
N/A
N/A
1M
128K
Pick GPT-5.5 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 is clearly ahead on the provisional aggregate, 89 to 78. 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 agentic, where it averages 81.8 against 54.6. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 82.7% to 50.8%. 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 is also the more expensive model on tokens at $5.00 input / $30.00 output per 1M tokens, versus $0.60 input / $3.00 output per 1M tokens for Kimi K2.5 (Reasoning). That is roughly 10.0x on output cost alone. GPT-5.5 gives you the larger context window at 1M, compared with 128K for Kimi K2.5 (Reasoning).
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 89 to 78. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 82.7% and 50.8%.
Kimi K2.5 (Reasoning) has the edge for knowledge tasks in this comparison, averaging 87.3 versus 66.4. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Kimi K2.5 (Reasoning) has the edge for coding in this comparison, averaging 76.8 versus 58.6. GPT-5.5 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 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 agentic tasks in this comparison, averaging 81.8 versus 54.6. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Kimi K2.5 (Reasoning) has the edge for multimodal and grounded tasks in this comparison, averaging 78.5 versus 69. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
For engineers, researchers, and the plain curious — a weekly brief on new models, ranking shifts, and pricing changes.
Free. No spam. Unsubscribe anytime.