Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
86
GPT-5.5
91
Verified leaderboard positions: GPT-5.3 Codex unranked · GPT-5.5 #5
Pick GPT-5.5 if you want the stronger benchmark profile. GPT-5.3 Codex only becomes the better choice if coding is the priority or you want the cheaper token bill.
Agentic
+10.0 difference
Coding
+4.5 difference
GPT-5.3 Codex
GPT-5.5
$1.75 / $14
$5 / $30
79 t/s
N/A
88.26s
N/A
400K
1M
Pick GPT-5.5 if you want the stronger benchmark profile. GPT-5.3 Codex 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 86. 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 71.5. The single biggest benchmark swing on the page is OSWorld-Verified, 64.7% to 78.7%. GPT-5.3 Codex 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 $1.75 input / $14.00 output per 1M tokens for GPT-5.3 Codex. That is roughly 2.1x on output cost alone. GPT-5.5 gives you the larger context window at 1M, compared with 400K for GPT-5.3 Codex.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 91 to 86. The biggest single separator in this matchup is OSWorld-Verified, where the scores are 64.7% and 78.7%.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 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 71.5. Inside this category, GDPval-AA is the benchmark that creates the most daylight between them.
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