Head-to-head comparison across 1benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
87
Grok 4.3
79
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok 4.3 only becomes the better choice if you want the cheaper token bill or you need the larger 1M context window.
Coding
+15.8 difference
GPT-5.3 Codex
Grok 4.3
$1.75 / $14
$1.25 / $2.5
79 t/s
209 t/s
88.26s
12.36s
400K
1M
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok 4.3 only becomes the better choice if you want the cheaper token bill or you need the larger 1M context window.
GPT-5.3 Codex is clearly ahead on the provisional aggregate, 87 to 79. 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 47.3.
GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $1.25 input / $2.50 output per 1M tokens for Grok 4.3. That is roughly 5.6x on output cost alone. Grok 4.3 gives you the larger context window at 1M, compared with 400K for GPT-5.3 Codex.
GPT-5.3 Codex is ahead on BenchLM's provisional leaderboard, 87 to 79.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 versus 47.3. Grok 4.3 stays close enough that the answer can still flip depending on your workload.
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