Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
89
Grok Code Fast 1
42
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok Code Fast 1 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
Coding
+7.7 difference
GPT-5.3 Codex
Grok Code Fast 1
$2.5 / $10
$null / $null
79 t/s
172 t/s
88.26s
2.81s
400K
256K
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok Code Fast 1 only becomes the better choice if coding is the priority or you would rather avoid the extra latency and token burn of a reasoning model.
GPT-5.3 Codex is clearly ahead on the provisional aggregate, 89 to 42. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.3 Codex is the reasoning model in the pair, while Grok Code Fast 1 is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5.3 Codex gives you the larger context window at 400K, compared with 256K for Grok Code Fast 1.
GPT-5.3 Codex is ahead on BenchLM's provisional leaderboard, 89 to 42. The biggest single separator in this matchup is SWE-bench Verified, where the scores are 85% and 70.8%.
Grok Code Fast 1 has the edge for coding in this comparison, averaging 70.8 versus 63.1. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.
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