Gemini 2.5 Flash vs Grok 4.20 (Reasoning) vs DeepSeek-V3.1
Too close to call on our weighted score (Grok 4.20 (Reasoning) 68, Gemini 2.5 Flash 68, DeepSeek-V3.1 55). The right pick depends on what you value most.
GoogleGemini 2.5 Flash
68/100- ECI140.8
- Price$0.30 / $2.50
- Context1.05M
xAIGrok 4.20 (Reasoning)
68/100- ECI152.0
- Price$1.25 / $2.50
- Context1M
DeepSeekDeepSeek-V3.1
55/100- ECI139.9
- Price$0.385 / $1.25
- Context131K
Too close to call
It is close. Our weighted score puts them within a point (Grok 4.20 (Reasoning) 68/100, Gemini 2.5 Flash 68/100, DeepSeek-V3.1 55/100), so choose by what matters most for your work: Grok 4.20 (Reasoning) for raw capability, DeepSeek-V3.1 on price and Gemini 2.5 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGrok 4.20 (Reasoning)Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 · Gemini 2.5 Flash 140.8 · DeepSeek-V3.1 139.9
- Lowest priceDeepSeek-V3.1DeepSeek-V3.1 $0.601 · Gemini 2.5 Flash $0.85 · Grok 4.20 (Reasoning) $1.56 per 1M tokens (3:1 blend)
- Longest contextGemini 2.5 FlashGemini 2.5 Flash 1,048,576 · Grok 4.20 (Reasoning) 1,000,000 · DeepSeek-V3.1 131,072 tokens
- Widest inputsGemini 2.5 FlashGemini 2.5 Flash: Text, Images, PDFs, Audio, Video · Grok 4.20 (Reasoning): Text, Images, PDFs · DeepSeek-V3.1: Text
- Self-hostingDeepSeek-V3.1Publishes downloadable weights (MIT License)
| Measure | Weight | Gemini 2.5 Flash | Grok 4.20 (Reasoning) | DeepSeek-V3.1 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 67 | 81 | 65 |
| Price | 25% | 53 | 41 | 60 |
| Inputs & features | 15% | 100 | 80 | 35 |
| Context window | 10% | 61 | 60 | 24 |
| Overall | 100% | 68/100 | 68/100 | 55/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 2.5 FlashGoogle | Grok 4.20 (Reasoning)xAI | DeepSeek-V3.1DeepSeek |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 140.8 | 152.0 (best) | 139.9 |
| ECI rank | #97 of 148 | #41 of 148 (best) | #100 of 148 |
| GPQA DiamondGraduate-level science questions | — | 89.3% | — |
| FrontierMath Tiers 1–3Research-level mathematics | — | 44.9% | — |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 92.2% | — |
| SimpleQA VerifiedShort factual questions | — | 30.2% | — |
| Price per million tokens | |||
| Input | $0.30 (best) | $1.25 | $0.385 |
| Output | $2.50 | $2.50 | $1.25 (best) |
| Cached input | $0.03 (best) | $0.20 | — |
| Blended (3:1) | $0.85 | $1.56 | $0.601 (best) |
| Long-context rate | Same rate | Over 200K: $2.50 / $5.00 | Same rate |
| Price source | Official Google API | Official xAI API | Median of 8 providers |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 1,000,000 tokens | 131,072 tokens |
| Max output | 65,536 tokens (best) | 30,000 tokens | 8,192 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | No |
| PDFs | Yes | Yes | No |
| Audio | Yes | No | No |
| Video | Yes | No | No |
| Reasoning | Yes | Yes | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | No |
| Availability | |||
| Weights | Proprietary | Proprietary | OpenMIT License |
| API model ID | gemini-2.5-flash | grok-4.20-0309-reasoning | — |
| API providers | 22 (best) | 11 | 8 |
| Released | Jun 17, 2025 | Mar 9, 2026 | Aug 21, 2025 |
| Knowledge cutoff | Jan 2025 | — | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 2.5 Flash$8.00
- Grok 4.20 (Reasoning)$17.50
- DeepSeek-V3.1$6.35
Which should you choose?
Which is better: Gemini 2.5 Flash, Grok 4.20 (Reasoning) or DeepSeek-V3.1?
It is close. Our weighted score puts them within a point (Grok 4.20 (Reasoning) 68/100, Gemini 2.5 Flash 68/100, DeepSeek-V3.1 55/100), so choose by what matters most for your work: Grok 4.20 (Reasoning) for raw capability, DeepSeek-V3.1 on price and Gemini 2.5 Flash for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 2.5 Flash, Grok 4.20 (Reasoning) or DeepSeek-V3.1?
DeepSeek-V3.1 is cheaper at $0.385 input / $1.25 output per million tokens (median across 8 API providers). Gemini 2.5 Flash costs $0.30 input / $2.50 output per million tokens (official Google API price); Grok 4.20 (Reasoning) costs $1.25 input / $2.50 output per million tokens (official xAI API price). At a typical mix of three input tokens to one output token, that is $0.601 per million tokens for DeepSeek-V3.1 versus $0.85 for Gemini 2.5 Flash (1.4× as much) and $1.56 for Grok 4.20 (Reasoning) (2.6× as much).
Which scores higher on benchmarks?
Grok 4.20 (Reasoning) scores higher on the Capabilities Index (ECI): Grok 4.20 (Reasoning) 152.0 (#41 of 148), Gemini 2.5 Flash 140.8 (#97 of 148) and DeepSeek-V3.1 139.9 (#100 of 148). Their confidence ranges do not overlap (149.3–154.4 vs 138.5–142.3), so the gap is a real one.
Which is better for coding?
There are no published SWE-bench Verified results for Gemini 2.5 Flash, Grok 4.20 (Reasoning) and DeepSeek-V3.1 yet, so there is no like-for-like coding score. On overall capability, Grok 4.20 (Reasoning) leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Gemini 2.5 Flash has the largest context window at 1,048,576 tokens, against 1,000,000 for Grok 4.20 (Reasoning) and 131,072 for DeepSeek-V3.1. Maximum output per response: Gemini 2.5 Flash up to 65,536, Grok 4.20 (Reasoning) up to 30,000, DeepSeek-V3.1 up to 8,192 tokens.
Which can read images, PDFs, audio or video?
Gemini 2.5 Flash accepts text, images, PDFs, audio and video; Grok 4.20 (Reasoning) accepts text, images and PDFs; DeepSeek-V3.1 accepts text. Gemini 2.5 Flash handles the widest range of inputs.
Are any of these open source?
DeepSeek-V3.1 publishes its weights (MIT License) and can be self-hosted; Gemini 2.5 Flash and Grok 4.20 (Reasoning) is proprietary.
Which is newer?
Grok 4.20 (Reasoning) is the newest, released Mar 9, 2026. DeepSeek-V3.1 came out Aug 21, 2025; Gemini 2.5 Flash came out Jun 17, 2025. Knowledge cutoff: Gemini 2.5 Flash Jan 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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