Head-to-head comparison across 4benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
GPT-5.5
91
Grok 4.20
72
Verified leaderboard positions: GPT-5.5 #5 · Grok 4.20 unranked
Pick GPT-5.5 if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if coding is the priority or you want the cheaper token bill.
Agentic
+34.4 difference
Coding
+2.4 difference
Reasoning
+31.7 difference
Multimodal
+0.4 difference
GPT-5.5
Grok 4.20
$5 / $30
$2 / $6
N/A
233 t/s
N/A
10.33s
1M
2M
Pick GPT-5.5 if you want the stronger benchmark profile. Grok 4.20 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 72. 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 47.1. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 82% to 47.1%. Grok 4.20 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 $2.00 input / $6.00 output per 1M tokens for Grok 4.20. That is roughly 5.0x on output cost alone. Grok 4.20 gives you the larger context window at 2M, compared with 1M for GPT-5.5.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 91 to 72. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 82% and 47.1%.
Grok 4.20 has the edge for coding in this comparison, averaging 61 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 reasoning in this comparison, averaging 85 versus 53.3. Inside this category, ARC-AGI-2 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 47.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Grok 4.20 has the edge for multimodal and grounded tasks in this comparison, averaging 70.8 versus 70.4. Inside this category, MMMU-Pro 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.