Gemini 3.5 Flash vs Grok 4.20
Wins 7 of 8 areas
Coding · Agents · Reasoning · Facts · Images and charts · Math · Long documents
Wins 1 of 8 areas
Following instructions
Gemini 3.5 Flash is the stronger all-rounder.Grok 4.20 is cheaper and better at following instructions.
Scores updated · 23 tests both models report · How we compare
Where each one wins
Tests won in each of the eight areas we test. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- ReasoningHard problems that need careful thinking40Gemini 3.5 Flash4 of 4 tests
- AgentsCarrying out multi-step tasks on its own20Gemini 3.5 Flash2 of 2 tests
- MathCompetition and research-level math20Gemini 3.5 Flash2 of 2 tests
- FactsGetting facts right instead of making them up21Gemini 3.5 Flash2 of 3 tests
- CodingWriting and fixing software10Gemini 3.5 Flash1 of 2 tests · 1 tie
- Images and chartsUnderstanding pictures, charts and video10Gemini 3.5 Flash1 of 1 test
- Long documentsFinding answers in very long texts10Gemini 3.5 Flash1 of 1 test
- Following instructionsDoing exactly what it is asked01Grok 4.201 of 1 test
Images and charts, long documents and following instructions rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
Grok 4.20 costs 64% less for the same work.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Gemini 3.5 Flash pulls ahead
- Short factual questions, answered correctlySimpleQA Verified+36points ahead
- Long professional tasks in banking, consulting and lawAA ApexAgents+32.9points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+22.5points ahead
Where Grok 4.20 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+39.8points ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+6.6points ahead
Every test, side by side
All 23 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingGemini 3.5 Flash
- SciCodeGemini 3.5 Flash by 9.253.944.7+9.2
- Terminal-Bench Hardtie40.940.9tie
AgentsGemini 3.5 Flash
- AA ApexAgentsGemini 3.5 Flash by 32.947.114.2+32.9
- GDPValGemini 3.5 Flash by 8.235.227+8.2
ReasoningGemini 3.5 Flash
- Humanity's Last ExamGemini 3.5 Flash by 10.342.732.4+10.3
- CritPtGemini 3.5 Flash by 7.113.16+7.1
- ARC-AGI-2Gemini 3.5 Flash by 772.165.1+7
- GPQA DiamondGemini 3.5 Flash by 3.792.288.5+3.7
FactsGemini 3.5 Flash
- AA-Omniscience · Non-hallucinationGrok 4.20 by 39.837.877.6+39.8
- SimpleQA VerifiedGemini 3.5 Flash by 3666.230.2+36
- AA-Omniscience · AccuracyGemini 3.5 Flash by 22.551.428.9+22.5
Images and chartsGemini 3.5 Flash
- MMMU-ProGemini 3.5 Flash by 11.184.373.2+11.1
MathGemini 3.5 Flash
- FrontierMath Tiers 1-3 (v2)Gemini 3.5 Flash by 17.962.844.9+17.9
- FrontierMath Tier 4Gemini 3.5 Flash by 9.726.817.1+9.7
Following instructionsGrok 4.20
- IFBenchGrok 4.20 by 6.676.382.9+6.6
Other results7 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- Artificial Analysis Coding IndexGemini 3.5 Flash by 27.970.142.2+27.9
- AA Agentic IndexGrok 4.20 by 23.627.350.9+23.6
- AA-OmniscienceGemini 3.5 Flash by 8.221.212.9+8.2
- HiL-Bench (Tools-allowed)Gemini 3.5 Flash by 7.727.720+7.7
- AA IntelligenceGemini 3.5 Flash by 7.432.625.2+7.4
- ARC-AGI-1Gemini 3.5 Flash by 392.589.5+3
- τ²-Bench Telecom (AA run)Grok 4.20 by 1.295.396.5+1.2
Questions people ask
Which is better, Gemini 3.5 Flash or Grok 4.20?
Gemini 3.5 Flash wins seven of the eight areas we test: coding, agents, reasoning, facts, images and charts, math and long documents. Grok 4.20 wins following instructions, and costs 64% less.
Which is better for coding?
Gemini 3.5 Flash. It wins 1 of the 2 coding tests both models report; Grok 4.20 wins none, and 1 is a tie.
Which is cheaper?
Gemini 3.5 Flash costs $1.50 per million input tokens and $9.00 per million output tokens; Grok 4.20 costs $1.25 and $2.50. That makes Grok 4.20 about 64% cheaper for the same work.
How do you compare the two?
We use the 23 benchmark tests both models have published scores on. The verdict counts the 16 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 7 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.