Kimi K2.6 vs Gemini 3 Flash Preview vs Grok 4.20 (Reasoning)
Gemini 3 Flash Preview comes out ahead, 73 to 68 and 65 on our weighted score, and it is the cheaper option too.
Moonshot AIKimi K2.6
65/100- ECI151.1
- Price$0.95 / $4.00
- Context262K
- Our pick
GoogleGemini 3 Flash Preview
73/100- ECI151.8
- Price$0.50 / $3.00
- Context1.05M
xAIGrok 4.20 (Reasoning)
68/100- ECI152.0
- Price$1.25 / $2.50
- Context1M
Gemini 3 Flash Preview is our pick
Gemini 3 Flash Preview is the better all-round choice, scoring 73/100 against Grok 4.20 (Reasoning) (68) and Kimi K2.6 (65). It leads on price and inputs & features. 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 3 Flash Preview 151.8 · Kimi K2.6 151.1
- Lowest priceGemini 3 Flash PreviewGemini 3 Flash Preview $1.13 · Grok 4.20 (Reasoning) $1.56 · Kimi K2.6 $1.71 per 1M tokens (3:1 blend)
- Longest contextGemini 3 Flash PreviewGemini 3 Flash Preview 1,048,576 · Grok 4.20 (Reasoning) 1,000,000 · Kimi K2.6 262,144 tokens
- Widest inputsGemini 3 Flash PreviewKimi K2.6: Text, Images, Video · Gemini 3 Flash Preview: Text, Images, PDFs, Audio, Video · Grok 4.20 (Reasoning): Text, Images, PDFs
- Self-hostingKimi K2.6Publishes downloadable weights
| Measure | Weight | Kimi K2.6 | Gemini 3 Flash Preview | Grok 4.20 (Reasoning) |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 79 | 80 | 81 |
| Price | 25% | 39 | 47 | 41 |
| Inputs & features | 15% | 80 | 100 | 80 |
| Context window | 10% | 37 | 61 | 60 |
| Overall | 100% | 65/100 | 73/100 | 68/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Kimi K2.6Moonshot AI | Gemini 3 Flash PreviewGoogle | Grok 4.20 (Reasoning)xAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 151.1 | 151.8 | 152.0 (best) |
| ECI rank | #45 of 148 | #43 of 148 | #41 of 148 (best) |
| GPQA DiamondGraduate-level science questions | 90.8% (best) | 89.4% | 89.3% |
| FrontierMath Tiers 1–3Research-level mathematics | 57.2% (best) | 51.2% | 44.9% |
| OTIS Mock AIME 2024–2025Competition mathematics | 96.1% (best) | 95.6% | 92.2% |
| SWE-bench VerifiedFixing real GitHub issues | 76.7% (best) | 75.4% | — |
| SimpleQA VerifiedShort factual questions | 34.9% | 66.8% (best) | 30.2% |
| Price per million tokens | |||
| Input | $0.95 | $0.50 (best) | $1.25 |
| Output | $4.00 | $3.00 | $2.50 (best) |
| Cached input | $0.16 | $0.05 (best) | $0.20 |
| Blended (3:1) | $1.71 | $1.13 (best) | $1.56 |
| Long-context rate | Same rate | Same rate | Over 200K: $2.50 / $5.00 |
| Price source | Official Moonshot AI API | Official Google API | Official xAI API |
| Limits | |||
| Context window | 262,144 tokens | 1,048,576 tokens (best) | 1,000,000 tokens |
| Max output | 262,144 tokens (best) | 65,536 tokens | 30,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | No | Yes | Yes |
| Audio | No | Yes | No |
| Video | Yes | Yes | No |
| Reasoning | Yes | Yesminimal · low · medium · high | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Open | Proprietary | Proprietary |
| API model ID | kimi-k2.6 | gemini-3-flash-preview | grok-4.20-0309-reasoning |
| API providers | 46 (best) | 20 | 11 |
| Released | Apr 21, 2026 | Dec 17, 2025 | Mar 9, 2026 |
| Knowledge cutoff | Jan 2025 | 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.
- Kimi K2.6$17.50
- Gemini 3 Flash Preview$11.00
- Grok 4.20 (Reasoning)$17.50
Which should you choose?
Which is better: Kimi K2.6, Gemini 3 Flash Preview or Grok 4.20 (Reasoning)?
Gemini 3 Flash Preview is the better all-round choice, scoring 73/100 against Grok 4.20 (Reasoning) (68) and Kimi K2.6 (65). It leads on price and inputs & features. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Kimi K2.6, Gemini 3 Flash Preview or Grok 4.20 (Reasoning)?
Gemini 3 Flash Preview is cheaper at $0.50 input / $3.00 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); Kimi K2.6 costs $0.95 input / $4.00 output per million tokens (official Moonshot AI API price). At a typical mix of three input tokens to one output token, that is $1.13 per million tokens for Gemini 3 Flash Preview versus $1.56 for Grok 4.20 (Reasoning) (1.4× as much) and $1.71 for Kimi K2.6 (1.5× 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 3 Flash Preview 151.8 (#43 of 148) and Kimi K2.6 151.1 (#45 of 148). The confidence ranges of the top two overlap (149.3–154.4 vs 150.4–153.7), so treat the gap as small. On individual benchmarks: GPQA Diamond — Kimi K2.6 90.8%, Gemini 3 Flash Preview 89.4%, Grok 4.20 (Reasoning) 89.3%; FrontierMath Tiers 1–3 — Kimi K2.6 57.2%, Gemini 3 Flash Preview 51.2%, Grok 4.20 (Reasoning) 44.9%; OTIS Mock AIME 2024–2025 — Kimi K2.6 96.1%, Gemini 3 Flash Preview 95.6%, Grok 4.20 (Reasoning) 92.2%; SimpleQA Verified — Gemini 3 Flash Preview 66.8%, Kimi K2.6 34.9%, Grok 4.20 (Reasoning) 30.2%.
Which is better for coding?
There are no published SWE-bench Verified results for Grok 4.20 (Reasoning) 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 3 Flash Preview has the largest context window at 1,048,576 tokens, against 1,000,000 for Grok 4.20 (Reasoning) and 262,144 for Kimi K2.6. Maximum output per response: Kimi K2.6 up to 262,144, Gemini 3 Flash Preview up to 65,536, Grok 4.20 (Reasoning) up to 30,000 tokens.
Which can read images, PDFs, audio or video?
Kimi K2.6 accepts text, images and video; Gemini 3 Flash Preview accepts text, images, PDFs, audio and video; Grok 4.20 (Reasoning) accepts text, images and PDFs. Gemini 3 Flash Preview handles the widest range of inputs.
Are any of these open source?
Kimi K2.6 publishes its weights and can be self-hosted; Gemini 3 Flash Preview and Grok 4.20 (Reasoning) is proprietary.
Which is newer?
Kimi K2.6 is the newest, released Apr 21, 2026. Grok 4.20 (Reasoning) came out Mar 9, 2026; Gemini 3 Flash Preview came out Dec 17, 2025. Knowledge cutoff: Kimi K2.6 Jan 2025, Gemini 3 Flash Preview 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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