Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
Step 3.5 Flash finishes one point ahead overall, 66 to 65. 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.
Step 3.5 Flash's sharpest advantage is in mathematics, where it averages 84.5 against 75.9. The single biggest benchmark swing on the page is MMMU-Pro, 64 to 80. Seed 1.6 does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.
Seed 1.6 is also the more expensive model on tokens at $0.25 input / $2.00 output per 1M tokens, versus $0.10 input / $0.30 output per 1M tokens for Step 3.5 Flash. That is roughly 6.7x on output cost alone. Seed 1.6 is the reasoning model in the pair, while Step 3.5 Flash is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use.
Pick Step 3.5 Flash if you want the stronger benchmark profile. Seed 1.6 only becomes the better choice if multimodal & grounded is the priority or you want the stronger reasoning-first profile.
Step 3.5 Flash
60.2
Seed 1.6
62.3
Step 3.5 Flash
47.1
Seed 1.6
42.4
Step 3.5 Flash
66.7
Seed 1.6
79.6
Step 3.5 Flash
78.3
Seed 1.6
74.5
Step 3.5 Flash
60.8
Seed 1.6
56.4
Step 3.5 Flash
87
Seed 1.6
87
Step 3.5 Flash
82.8
Seed 1.6
83.4
Step 3.5 Flash
84.5
Seed 1.6
75.9
Step 3.5 Flash is ahead overall, 66 to 65. The biggest single separator in this matchup is MMMU-Pro, where the scores are 64 and 80.
Step 3.5 Flash has the edge for knowledge tasks in this comparison, averaging 60.8 versus 56.4. 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 42.4. 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 75.9. 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 74.5. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.
Seed 1.6 has the edge for agentic tasks in this comparison, averaging 62.3 versus 60.2. Inside this category, OSWorld-Verified is the benchmark that creates the most daylight between them.
Seed 1.6 has the edge for multimodal and grounded tasks in this comparison, averaging 79.6 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
Step 3.5 Flash and Seed 1.6 are effectively tied for instruction following here, both landing at 87 on average.
Seed 1.6 has the edge for multilingual tasks in this comparison, averaging 83.4 versus 82.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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