Grok 4.20 (Reasoning) vs GPT-5.4 mini vs Kimi K2.6
Grok 4.20 (Reasoning) comes out ahead, 68 to 65 and 63 on our weighted score, and it is the cheaper option too.
- Our pick
xAIGrok 4.20 (Reasoning)
68/100- ECI152.0
- Price$1.25 / $2.50
- Context1M
OpenAIGPT-5.4 mini
63/100- ECI148.8
- Price$0.75 / $4.50
- Context400K
Moonshot AIKimi K2.6
65/100- ECI151.1
- Price$0.95 / $4.00
- Context262K
Grok 4.20 (Reasoning) is our pick
Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against Kimi K2.6 (65) and GPT-5.4 mini (63). It leads on context window. 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 · Kimi K2.6 151.1 · GPT-5.4 mini 148.8
- Lowest priceGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) $1.56 · GPT-5.4 mini $1.69 · Kimi K2.6 $1.71 per 1M tokens (3:1 blend)
- Longest contextGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) 1,000,000 · GPT-5.4 mini 400,000 · Kimi K2.6 262,144 tokens
- Widest inputsGrok 4.20 (Reasoning) and Kimi K2.6Grok 4.20 (Reasoning): Text, Images, PDFs · GPT-5.4 mini: Text, Images · Kimi K2.6: Text, Images, Video
- Self-hostingKimi K2.6Publishes downloadable weights
| Measure | Weight | Grok 4.20 (Reasoning) | GPT-5.4 mini | Kimi K2.6 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 81 | 77 | 79 |
| Price | 25% | 41 | 39 | 39 |
| Inputs & features | 15% | 80 | 70 | 80 |
| Context window | 10% | 60 | 44 | 37 |
| Overall | 100% | 68/100 | 63/100 | 65/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Grok 4.20 (Reasoning)xAI | GPT-5.4 miniOpenAI | Kimi K2.6Moonshot AI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 152.0 (best) | 148.8 | 151.1 |
| ECI rank | #41 of 148 (best) | #56 of 148 | #45 of 148 |
| GPQA DiamondGraduate-level science questions | 89.3% | 86.9% | 90.8% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | 44.9% | 51.2% | 57.2% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 92.2% | 88.9% | 96.1% (best) |
| SWE-bench VerifiedFixing real GitHub issues | — | — | 76.7% |
| SimpleQA VerifiedShort factual questions | 30.2% | 29.4% | 34.9% (best) |
| Price per million tokens | |||
| Input | $1.25 | $0.75 (best) | $0.95 |
| Output | $2.50 (best) | $4.50 | $4.00 |
| Cached input | $0.20 | $0.075 (best) | $0.16 |
| Blended (3:1) | $1.56 (best) | $1.69 | $1.71 |
| Long-context rate | Over 200K: $2.50 / $5.00 | Same rate | Same rate |
| Price source | Official xAI API | Official OpenAI API | Official Moonshot AI API |
| Limits | |||
| Context window | 1,000,000 tokens (best) | 400,000 tokens | 262,144 tokens |
| Max output | 30,000 tokens | 128,000 tokens | 262,144 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | No |
| Audio | No | No | No |
| Video | No | No | Yes |
| Reasoning | Yes | Yeslow · medium · high · xhigh | Yes |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Open |
| API model ID | grok-4.20-0309-reasoning | gpt-5.4-mini | kimi-k2.6 |
| API providers | 11 | 29 | 46 (best) |
| Released | Mar 9, 2026 | Mar 17, 2026 | Apr 21, 2026 |
| Knowledge cutoff | — | Aug 31, 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.
- Grok 4.20 (Reasoning)$17.50
- GPT-5.4 mini$16.50
- Kimi K2.6$17.50
Which should you choose?
Which is better: Grok 4.20 (Reasoning), GPT-5.4 mini or Kimi K2.6?
Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against Kimi K2.6 (65) and GPT-5.4 mini (63). It leads on context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Grok 4.20 (Reasoning), GPT-5.4 mini or Kimi K2.6?
Grok 4.20 (Reasoning) is cheaper at $1.25 input / $2.50 output per million tokens (official xAI API price). GPT-5.4 mini costs $0.75 input / $4.50 output per million tokens (official OpenAI 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 $1.56 per million tokens for Grok 4.20 (Reasoning) versus $1.69 for GPT-5.4 mini (1.1× as much) and $1.71 for Kimi K2.6 (1.1× 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), Kimi K2.6 151.1 (#45 of 148) and GPT-5.4 mini 148.8 (#56 of 148). The confidence ranges of the top two overlap (149.3–154.4 vs 149.1–152.8), so treat the gap as small. On individual benchmarks: GPQA Diamond — Kimi K2.6 90.8%, Grok 4.20 (Reasoning) 89.3%, GPT-5.4 mini 86.9%; FrontierMath Tiers 1–3 — Kimi K2.6 57.2%, GPT-5.4 mini 51.2%, Grok 4.20 (Reasoning) 44.9%; OTIS Mock AIME 2024–2025 — Kimi K2.6 96.1%, Grok 4.20 (Reasoning) 92.2%, GPT-5.4 mini 88.9%; SimpleQA Verified — Kimi K2.6 34.9%, Grok 4.20 (Reasoning) 30.2%, GPT-5.4 mini 29.4%.
Which is better for coding?
There are no published SWE-bench Verified results for Grok 4.20 (Reasoning) and GPT-5.4 mini 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?
Grok 4.20 (Reasoning) has the largest context window at 1,000,000 tokens, against 400,000 for GPT-5.4 mini and 262,144 for Kimi K2.6. Maximum output per response: Grok 4.20 (Reasoning) up to 30,000, GPT-5.4 mini up to 128,000, Kimi K2.6 up to 262,144 tokens.
Which can read images, PDFs, audio or video?
Grok 4.20 (Reasoning) accepts text, images and PDFs; GPT-5.4 mini accepts text and images; Kimi K2.6 accepts text, images and video. Grok 4.20 (Reasoning) handles the widest range of inputs.
Are any of these open source?
Kimi K2.6 publishes its weights and can be self-hosted; Grok 4.20 (Reasoning) and GPT-5.4 mini is proprietary.
Which is newer?
Kimi K2.6 is the newest, released Apr 21, 2026. GPT-5.4 mini came out Mar 17, 2026; Grok 4.20 (Reasoning) came out Mar 9, 2026. Knowledge cutoff: GPT-5.4 mini Aug 31, 2025, Kimi K2.6 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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