Head-to-head comparison across 5benchmark categories. Overall scores shown here use BenchLM's provisional ranking lane.
Gemini 3.5 Flash
87
GPT-5.5
91
Verified leaderboard positions: Gemini 3.5 Flash #6 · GPT-5.5 #3
Pick GPT-5.5 if you want the stronger benchmark profile. Gemini 3.5 Flash only becomes the better choice if multimodal & grounded is the priority or you want the cheaper token bill.
Agentic
+4.3 difference
Coding
+4.1 difference
Reasoning
+10.3 difference
Knowledge
+8.4 difference
Multimodal
+13.4 difference
Gemini 3.5 Flash
GPT-5.5
$1.5 / $9
$5 / $30
284.2 t/s
N/A
18.55s
N/A
1M
1M
Pick GPT-5.5 if you want the stronger benchmark profile. Gemini 3.5 Flash only becomes the better choice if multimodal & grounded is the priority or you want the cheaper token bill.
GPT-5.5 is clearly ahead on the provisional aggregate, 91 to 87. 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 reasoning, where it averages 85 against 74.7. The single biggest benchmark swing on the page is ARC-AGI-2, 72.1% to 85%. Gemini 3.5 Flash does hit back in multimodal & grounded, 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 $1.50 input / $9.00 output per 1M tokens for Gemini 3.5 Flash. That is roughly 3.3x on output cost alone.
GPT-5.5 is ahead on BenchLM's provisional leaderboard, 91 to 87. The biggest single separator in this matchup is ARC-AGI-2, where the scores are 72.1% and 85%.
GPT-5.5 has the edge for knowledge tasks in this comparison, averaging 66.4 versus 58. Inside this category, HLE is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for coding in this comparison, averaging 58.6 versus 54.5. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
GPT-5.5 has the edge for reasoning in this comparison, averaging 85 versus 74.7. 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 77.2. Inside this category, MCP Atlas is the benchmark that creates the most daylight between them.
Gemini 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 83.8 versus 70.4. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
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