Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
Step 3.5 Flash is clearly ahead on the aggregate, 66 to 49. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Step 3.5 Flash's sharpest advantage is in coding, where it averages 47.1 against 21.7. The single biggest benchmark swing on the page is MuSR, 82 to 46. Gemini 2.5 Flash does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.
Gemini 2.5 Flash is also the more expensive model on tokens at $0.15 input / $0.60 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 2.0x on output cost alone. Gemini 2.5 Flash gives you the larger context window at 1M, compared with 256K for Step 3.5 Flash.
Pick Step 3.5 Flash if you want the stronger benchmark profile. Gemini 2.5 Flash only becomes the better choice if multimodal & grounded is the priority or you need the larger 1M context window.
Step 3.5 Flash
60.2
Gemini 2.5 Flash
46.5
Step 3.5 Flash
47.1
Gemini 2.5 Flash
21.7
Step 3.5 Flash
66.7
Gemini 2.5 Flash
67.7
Step 3.5 Flash
78.3
Gemini 2.5 Flash
59.2
Step 3.5 Flash
60.8
Gemini 2.5 Flash
40.5
Step 3.5 Flash
87
Gemini 2.5 Flash
79
Step 3.5 Flash
82.8
Gemini 2.5 Flash
70.8
Step 3.5 Flash
84.5
Gemini 2.5 Flash
59.4
Step 3.5 Flash is ahead overall, 66 to 49. The biggest single separator in this matchup is MuSR, where the scores are 82 and 46.
Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 40.5. Inside this category, MMLU is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for coding in this comparison, averaging 47.1 versus 21.7. Inside this category, HumanEval is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for math in this comparison, averaging 84.5 versus 59.4. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for reasoning in this comparison, averaging 78.3 versus 59.2. Inside this category, MuSR is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for agentic tasks in this comparison, averaging 60.2 versus 46.5. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
Gemini 2.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 67.7 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for instruction following in this comparison, averaging 87 versus 79. Inside this category, IFEval is the benchmark that creates the most daylight between them.
Step 3.5 Flash has the edge for multilingual tasks in this comparison, averaging 82.8 versus 70.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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