Gemini 3 Pro Deep Think vs Step 3.5 Flash

Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.

Gemini 3 Pro Deep Think is clearly ahead on the aggregate, 81 to 66. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Gemini 3 Pro Deep Think's sharpest advantage is in multimodal & grounded, where it averages 95 against 66.7. The single biggest benchmark swing on the page is MMMU-Pro, 95 to 64.

Gemini 3 Pro Deep Think 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. Gemini 3 Pro Deep Think gives you the larger context window at 2M, compared with 256K for Step 3.5 Flash.

Quick Verdict

Pick Gemini 3 Pro Deep Think if you want the stronger benchmark profile. Step 3.5 Flash only becomes the better choice if you would rather avoid the extra latency and token burn of a reasoning model.

Agentic

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

78.1

Step 3.5 Flash

60.2

77
Terminal-Bench 2.0
62
87
BrowseComp
66
73
OSWorld-Verified
54

Coding

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

60.3

Step 3.5 Flash

47.1

91
HumanEval
77
58
SWE-bench Verified
48
58
LiveCodeBench
45
63
SWE-bench Pro
49

Multimodal & Grounded

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

95

Step 3.5 Flash

66.7

95
MMMU-Pro
64
95
OfficeQA Pro
70

Reasoning

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

94.5

Step 3.5 Flash

78.3

95
SimpleQA
82
93
MuSR
82
95
BBH
83
94
LongBench v2
74
96
MRCRv2
73

Knowledge

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

74.7

Step 3.5 Flash

60.8

99
MMLU
84
97
GPQA
83
95
SuperGPQA
81
93
OpenBookQA
79
81
MMLU-Pro
76
32
HLE
12
88
FrontierScience
71

Instruction Following

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

89

Step 3.5 Flash

87

89
IFEval
87

Multilingual

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

87.4

Step 3.5 Flash

82.8

92
MGSM
86
85
MMLU-ProX
81

Mathematics

Gemini 3 Pro Deep Think

Gemini 3 Pro Deep Think

94.5

Step 3.5 Flash

84.5

99
AIME 2023
85
99
AIME 2024
87
98
AIME 2025
86
95
HMMT Feb 2023
81
97
HMMT Feb 2024
83
96
HMMT Feb 2025
82
96
BRUMO 2025
84
92
MATH-500
85

Frequently Asked Questions

Which is better, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think is ahead overall, 81 to 66. The biggest single separator in this matchup is MMMU-Pro, where the scores are 95 and 64.

Which is better for knowledge tasks, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for knowledge tasks in this comparison, averaging 74.7 versus 60.8. Inside this category, HLE is the benchmark that creates the most daylight between them.

Which is better for coding, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for coding in this comparison, averaging 60.3 versus 47.1. Inside this category, HumanEval is the benchmark that creates the most daylight between them.

Which is better for math, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for math in this comparison, averaging 94.5 versus 84.5. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.

Which is better for reasoning, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for reasoning in this comparison, averaging 94.5 versus 78.3. Inside this category, MRCRv2 is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for agentic tasks in this comparison, averaging 78.1 versus 60.2. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for multimodal and grounded tasks in this comparison, averaging 95 versus 66.7. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for instruction following in this comparison, averaging 89 versus 87. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, Gemini 3 Pro Deep Think or Step 3.5 Flash?

Gemini 3 Pro Deep Think has the edge for multilingual tasks in this comparison, averaging 87.4 versus 82.8. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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