Head-to-head comparison across 2benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Gemini 3.5 Flash
88
GPT-5.3 Codex
87
Verified leaderboard positions: Gemini 3.5 Flash #7 · GPT-5.3 Codex unranked
Pick Gemini 3.5 Flash if you want the stronger benchmark profile. GPT-5.3 Codex only becomes the better choice if coding is the priority.
Agentic
+5.7 difference
Coding
+8.6 difference
Gemini 3.5 Flash
GPT-5.3 Codex
$1.5 / $9
$1.75 / $14
284.2 t/s
79 t/s
18.55s
88.26s
1M
400K
Pick Gemini 3.5 Flash if you want the stronger benchmark profile. GPT-5.3 Codex only becomes the better choice if coding is the priority.
Gemini 3.5 Flash finishes one point ahead on BenchLM's provisional leaderboard, 88 to 87. That is enough to call, but not enough to treat as a blowout. This matchup comes down to a few meaningful edges rather than one model dominating the board.
Gemini 3.5 Flash's sharpest advantage is in agentic, where it averages 77.2 against 71.5. The single biggest benchmark swing on the page is OSWorld-Verified, 78.4% to 64.7%. GPT-5.3 Codex does hit back in coding, so the answer changes if that is the part of the workload you care about most.
GPT-5.3 Codex is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $1.50 input / $9.00 output per 1M tokens for Gemini 3.5 Flash. Gemini 3.5 Flash gives you the larger context window at 1M, compared with 400K for GPT-5.3 Codex.
Gemini 3.5 Flash is ahead on BenchLM's provisional leaderboard, 88 to 87. The biggest single separator in this matchup is OSWorld-Verified, where the scores are 78.4% and 64.7%.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 63.1 versus 54.5. Inside this category, SWE-bench Pro is the benchmark that creates the most daylight between them.
Gemini 3.5 Flash has the edge for agentic tasks in this comparison, averaging 77.2 versus 71.5. Inside this category, OSWorld-Verified is the benchmark that creates the most daylight between them.
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