Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
88
o3-mini
56
Pick GPT-5.3 Codex if you want the stronger benchmark profile. o3-mini only becomes the better choice if you want the cheaper token bill.
Coding
+13.8 difference
GPT-5.3 Codex
o3-mini
$1.75 / $14
$1.1 / $4.4
79 t/s
160 t/s
88.26s
7.12s
400K
200K
Pick GPT-5.3 Codex if you want the stronger benchmark profile. o3-mini only becomes the better choice if you want the cheaper token bill.
GPT-5.3 Codex is clearly ahead on the provisional aggregate, 88 to 56. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.3 Codex's sharpest advantage is in coding, where it averages 63.1 against 49.3. The single biggest benchmark swing on the page is SWE-bench Verified, 85% to 49.3%.
GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $1.10 input / $4.40 output per 1M tokens for o3-mini. That is roughly 3.2x on output cost alone. GPT-5.3 Codex gives you the larger context window at 400K, compared with 200K for o3-mini.
GPT-5.3 Codex is ahead on BenchLM's provisional leaderboard, 88 to 56. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 85% and 49.3%.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 versus 49.3. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
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