Head-to-head comparison across 3benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GLM-5.1
83
GPT-5.5
91
Verified leaderboard positions: GLM-5.1 #21 · GPT-5.5 #3
Pick GPT-5.5 if you want the stronger benchmark profile. GLM-5.1 only becomes the better choice if coding is the priority or you want the cheaper token bill.
Agentic
+16.2 difference
Coding
+2.3 difference
Knowledge
+14.1 difference
GLM-5.1
GPT-5.5
$1.4 / $4.4
$5 / $30
N/A
N/A
N/A
N/A
203K
1M
Pick GPT-5.5 if you want the stronger benchmark profile. GLM-5.1 only becomes the better choice if coding is the priority or you want the cheaper token bill.
GPT-5.5 is clearly ahead on the provisional aggregate, 91 to 83. 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 81.5 against 65.3. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 63.5% to 82%. GLM-5.1 does hit back in coding, 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 $1.40 input / $4.40 output per 1M tokens for GLM-5.1. That is roughly 6.8x on output cost alone. GPT-5.5 gives you the larger context window at 1M, compared with 203K for GLM-5.1.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 91 to 83. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 63.5% and 82%.
GPT-5.5 has the edge for knowledge tasks in this comparison, averaging 66.4 versus 52.3. Inside this category, GPQA-D is the benchmark that creates the most daylight between them.
GLM-5.1 has the edge for coding in this comparison, averaging 60.9 versus 58.6. Inside this category, Vibe Code Bench is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for agentic tasks in this comparison, averaging 81.5 versus 65.3. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Estimates at 50,000 req/day · 1000 tokens/req average.
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