Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.3 Codex
87
Grok 4.20
73
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if you want the cheaper token bill or you need the larger 2M context window.
Agentic
+24.4 difference
Coding
+2.1 difference
GPT-5.3 Codex
Grok 4.20
$1.75 / $14
$2 / $6
79 t/s
233 t/s
88.26s
10.33s
400K
2M
Pick GPT-5.3 Codex if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if you want the cheaper token bill or you need the larger 2M context window.
GPT-5.3 Codex is clearly ahead on the provisional aggregate, 87 to 73. 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 agentic, where it averages 71.5 against 47.1. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 77.3% to 47.1%.
GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $2.00 input / $6.00 output per 1M tokens for Grok 4.20. That is roughly 2.3x on output cost alone. Grok 4.20 gives you the larger context window at 2M, compared with 400K for GPT-5.3 Codex.
GPT-5.3 Codex is ahead on BenchLM's provisional leaderboard, 87 to 73. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 77.3% and 47.1%.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 versus 61. Inside this category, Vibe Code Bench is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for agentic tasks in this comparison, averaging 71.5 versus 47.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
For engineers, researchers, and the plain curious — a weekly brief on new models, ranking shifts, and pricing changes.
Free. No spam. Unsubscribe anytime.