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Model comparison

Gemini 3.5 Flash vs Grok 4.20

Data verified

Head-to-head evidence from 9 shared benchmark results across 5 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.

64.75/100
Margin
10.1pts
← winning
54.68/100
3 category wins1 category wins

Public leaderboard positions: Gemini 3.5 Flash #33 (Estimated); Grok 4.20 #88 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.

Evidence parity. Gemini 3.5 Flash and Grok 4.20 share 9 comparable benchmark results. 4 of 8 categories are comparable. 37 results are unique to Gemini 3.5 Flash; 9 to Grok 4.20.

Updated July 23, 2026
Shared results
9
Gemini 3.5 Flash only
37
Grok 4.20 only
9
Comparable categories
4 / 8

Pick Gemini 3.5 Flash if you want the stronger benchmark profile. Grok 4.20 only becomes the better choice if coding is the priority or you want the cheaper token bill.

Confidence note. This is a partial-evidence comparison with 9 shared benchmark results across 5 evidence categories; 4 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.

Why this result

Gemini 3.5 Flash is clearly ahead on the BenchAlign aggregate, 64.75 to 54.68. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Gemini 3.5 Flash's sharpest advantage is in agentic, where it averages 77.2 against 47.1. The single biggest benchmark swing on the page is Terminal-Bench 2.0, 76.2% to 47.1%. Grok 4.20 does hit back in coding, so the answer changes if that is the part of the workload you care about most.

Gemini 3.5 Flash is also the more expensive model on tokens at $1.50 input / $9.00 output per 1M tokens, versus $2.00 input / $6.00 output per 1M tokens for Grok 4.20. Grok 4.20 gives you the larger context window at 2M, compared with 1M for Gemini 3.5 Flash.

Category breakdown

Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.

Category scores and score margins for Gemini 3.5 Flash and Grok 4.20
CategoryGemini 3.5 FlashΔGrok 4.20
AgenticGemini 3.5 Flash77.2Margin← 30.1Grok 4.2047.1
ReasoningGemini 3.5 Flash74.7Margin← 21.4Grok 4.2053.3
MultimodalGemini 3.5 Flash83.8Margin← 13.7Grok 4.2070.1
CodingGemini 3.5 Flash53.9Margin→ 13.2Grok 4.2067.1
KnowledgeGemini 3.5 Flash47.2MarginNo overlapGrok 4.20Not measured
MathGemini 3.5 Flash32.9MarginNo overlapGrok 4.20Not measured
Inst. FollowingGemini 3.5 Flash76.3MarginNo overlapGrok 4.20Not measured

Decisive benchmark drivers

The largest measured benchmark gaps in this matchup, with exact reported values.

More
A · Gemini 3.5 FlashB · Grok 4.20

  1. Terminal-Bench 2.0

    Agentic
    Source ↗
    A 76.2%B 47.1%
    Winner: Gemini 3.5 FlashΔ 29.1
    Terminal-Bench 2.0: Gemini 3.5 Flash scored 76.2%; Grok 4.20 scored 47.1%. Gemini 3.5 Flash wins this benchmark.

  2. CharXiv

    Multimodal
    Source ↗
    A 84.2%B 60.9%
    Winner: Gemini 3.5 FlashΔ 23.3
    CharXiv: Gemini 3.5 Flash scored 84.2%; Grok 4.20 scored 60.9%. Gemini 3.5 Flash wins this benchmark.

  3. ARC-AGI-2

    Reasoning
    Source ↗
    A 72.1%B 53.3%
    Winner: Gemini 3.5 FlashΔ 18.8
    ARC-AGI-2: Gemini 3.5 Flash scored 72.1%; Grok 4.20 scored 53.3%. Gemini 3.5 Flash wins this benchmark.

  4. MMMU-Pro

    Multimodal
    Source ↗
    A 83.6%B 75.2%
    Winner: Gemini 3.5 FlashΔ 8.4
    MMMU-Pro: Gemini 3.5 Flash scored 83.6%; Grok 4.20 scored 75.2%. Gemini 3.5 Flash wins this benchmark.

  5. SWE-bench Pro

    Coding
    Source ↗
    A 55.1%B 51.8%
    Winner: Gemini 3.5 FlashΔ 3.3
    SWE-bench Pro: Gemini 3.5 Flash scored 55.1%; Grok 4.20 scored 51.8%. Gemini 3.5 Flash wins this benchmark.

Operational comparison

Runtime and commercial metrics are compared only when both models have a complete sourced value.

MetricGemini 3.5 FlashGrok 4.20Comparison
Input / output priceUSD per 1M tokensGemini 3.5 Flash$1.5 input / $9 outputGrok 4.20$2 input / $6 outputGrok 4.20 has the lower combined listed price.
Generation speedtokens per secondGemini 3.5 Flash284.2 tok/sGrok 4.20233 tok/sGemini 3.5 Flash has the higher measured throughput.
First-answer latencyseconds to first tokenGemini 3.5 Flash18.55 sGrok 4.2010.33 sGrok 4.20 reaches the first token sooner.
Context windowmaximum listed tokensGemini 3.5 Flash1MGrok 4.202MGrok 4.20 lists the larger context window.

Benchmark Deep Dive

AgenticGemini 3.5 Flash wins
BenchmarkGemini 3.5 FlashGrok 4.20Result
Terminal-Bench 2.0Source 76.2%47.1%Gemini 3.5 Flash leads
MCP AtlasSource 83.6%—Not comparable
ToolathlonSource 56.5%—Not comparable
OSWorld-VerifiedSource 78.4%—Not comparable
Finance Agent v2Source 57.9%—Not comparable
GDPval-AASource 1349—Not comparable
τ²-bench resultsSource 95.3%—Not comparable
GDPval-AASource 42.4%—Not comparable
AA Agentic IndexSource 37.5%—Not comparable
APEX-Agents-AASource 47.1%—Not comparable
Gert LabsSource 61.85%38.36%Gemini 3.5 Flash leads
ResearchClawBenchSource 18.0%—Not comparable
AA AutomationBenchSource 42.6%—Not comparable
AA EnterpriseOps-GymSource 50.1%—Not comparable
terminalBenchHardSource 40.9%—Not comparable
DeepSearchQASource —62.8%Not comparable
CodingGrok 4.20 wins
BenchmarkGemini 3.5 FlashGrok 4.20Result
Terminal-Bench 2.0Source 76.2%—Not comparable
SWE-bench ProSource 55.1%51.8%Gemini 3.5 Flash leads
SciCodeSource 53.1%—Not comparable
Vibe Code BenchSource 48.68%4.06%Gemini 3.5 Flash leads
cursorBench31Source 49.8%—Not comparable
cursorBench32Source 48.8%—Not comparable
AA Coding IndexSource 70.1%—Not comparable
AA-SciCodeSource 53.1%—Not comparable
LiveCodeBench ProSource —74.2%Not comparable
SWE-bench VerifiedSource —76.7%Not comparable
ReasoningGemini 3.5 Flash wins
BenchmarkGemini 3.5 FlashGrok 4.20Result
MRCRv2Source 77.3%—Not comparable
MRCR 1MSource 26.6%—Not comparable
ARC-AGI-2Source 72.1%53.3%Gemini 3.5 Flash leads
AA-LCRSource 69.3%—Not comparable
CritPtSource 13.1%—Not comparable
Knowledge
BenchmarkGemini 3.5 FlashGrok 4.20Result
Artificial Analysis Intelligence IndexSource 50.2%—Not comparable
GPQASource 92.2%—Not comparable
GPQA-DSource 92.7%88.5%Gemini 3.5 Flash leads
HLESource 40.2%—Not comparable
AA-Omniscience AccuracySource 51.9%—Not comparable
AA-Omniscience Hallucination RateSource 60.7%—Not comparable
AA-GPQA DiamondSource 92.2%—Not comparable
AA-HLESource 41.0%—Not comparable
AA-Omniscience IndexSource 22.7%—Not comparable
HLE w/o toolsSource —31.6%Not comparable
HealthBench HardSource —20.3%Not comparable
MedXpertQA (Text)Source —50.2%Not comparable
Math
BenchmarkGemini 3.5 FlashGrok 4.20Result
FrontierMath v2 (Tiers 1-3)Source 38.966%—Not comparable
FrontierMath v2 (Tier 4)Source 14.583%—Not comparable
MultimodalGemini 3.5 Flash wins
BenchmarkGemini 3.5 FlashGrok 4.20Result
CharXivSource 84.2%60.9%Gemini 3.5 Flash leads
MMMU-ProSource 83.6%75.2%Gemini 3.5 Flash leads
Blueprint-Bench 2Source 33.6%—Not comparable
AA-MMMU-ProSource 84.3%—Not comparable
Design Arena WebsiteSource 12851257Gemini 3.5 Flash leads
ERQASource —54.1%Not comparable
SimpleVQASource —57.4%Not comparable
MedXpertQA (MM)Source —65.8%Not comparable
Inst. Following
BenchmarkGemini 3.5 FlashGrok 4.20Result
IFBenchSource 76.3%—Not comparable
AA-IFBenchSource 76.3%—Not comparable
Frequently Asked Questions (5)

Which is better, Gemini 3.5 Flash or Grok 4.20?

Gemini 3.5 Flash is ahead on BenchLM's BenchAlign leaderboard, 64.75 to 54.68. The biggest single separator in this matchup is Terminal-Bench 2.0, where the scores are 76.2% and 47.1%.

Which is better for coding, Gemini 3.5 Flash or Grok 4.20?

Grok 4.20 has the edge for coding in this comparison, averaging 67.1 versus 53.9. Inside this category, Vibe Code Bench is the benchmark that creates the most daylight between them.

Which is better for reasoning, Gemini 3.5 Flash or Grok 4.20?

Gemini 3.5 Flash has the edge for reasoning in this comparison, averaging 74.7 versus 53.3. Inside this category, ARC-AGI-2 is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, Gemini 3.5 Flash or Grok 4.20?

Gemini 3.5 Flash has the edge for agentic tasks in this comparison, averaging 77.2 versus 47.1. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, Gemini 3.5 Flash or Grok 4.20?

Gemini 3.5 Flash has the edge for multimodal and grounded tasks in this comparison, averaging 83.8 versus 70.1. Inside this category, Design Arena Website is the benchmark that creates the most daylight between them.

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