Claude Sonnet 3.5 v2 vs Grok 4.20 (Reasoning)
Grok 4.20 (Reasoning) comes out ahead, 68 to 44 on our weighted score, and it is the cheaper option too.
AnthropicClaude Sonnet 3.5 v2
44/100- ECI133.5
- Price$3.00 / $15.00
- Context200K
- Our pick
xAIGrok 4.20 (Reasoning)
68/100- ECI152.0
- Price$1.25 / $2.50
- Context1M
Add a model
Make it a three-way comparison.
Grok 4.20 (Reasoning) is our pick
Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against Claude Sonnet 3.5 v2 (44). It leads on capability, price, inputs & features and 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 · Claude Sonnet 3.5 v2 133.5
- Lowest priceGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) $1.56 · Claude Sonnet 3.5 v2 $6.00 per 1M tokens (3:1 blend)
- Longest contextGrok 4.20 (Reasoning)Grok 4.20 (Reasoning) 1,000,000 · Claude Sonnet 3.5 v2 200,000 tokens
- Widest inputsSame inputsClaude Sonnet 3.5 v2: Text, Images, PDFs · Grok 4.20 (Reasoning): Text, Images, PDFs
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | Claude Sonnet 3.5 v2 | Grok 4.20 (Reasoning) |
|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 57 | 81 |
| Price | 25% | 13 | 41 |
| Inputs & features | 15% | 60 | 80 |
| Context window | 10% | 32 | 60 |
| Overall | 100% | 44/100 | 68/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Claude Sonnet 3.5 v2Anthropic | Grok 4.20 (Reasoning)xAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | 133.5 | 152.0 (best) |
| ECI rank | #119 of 148 | #41 of 148 (best) |
| GPQA DiamondGraduate-level science questions | 55.3% | 89.3% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | — | 44.9% |
| OTIS Mock AIME 2024–2025Competition mathematics | 8.5% | 92.2% (best) |
| SimpleQA VerifiedShort factual questions | — | 30.2% |
| Price per million tokens | ||
| Input | $3.00 | $1.25 (best) |
| Output | $15.00 | $2.50 (best) |
| Cached input | — | $0.20 |
| Blended (3:1) | $6.00 | $1.56 (best) |
| Long-context rate | Same rate | Over 200K: $2.50 / $5.00 |
| Price source | Median of 1 providers | Official xAI API |
| Limits | ||
| Context window | 200,000 tokens | 1,000,000 tokens (best) |
| Max output | 8,192 tokens | 30,000 tokens (best) |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | Yes | Yes |
| PDFs | Yes | Yes |
| Audio | No | No |
| Video | No | No |
| Reasoning | No | Yes |
| Tool calling | Yes | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | — | grok-4.20-0309-reasoning |
| API providers | 1 | 11 (best) |
| Released | Oct 22, 2024 | Mar 9, 2026 |
| Knowledge cutoff | Apr 30, 2024 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Claude Sonnet 3.5 v2$60.00
- Grok 4.20 (Reasoning)$17.50
Which should you choose?
Which is better: Claude Sonnet 3.5 v2 or Grok 4.20 (Reasoning)?
Grok 4.20 (Reasoning) is the better all-round choice, scoring 68/100 against Claude Sonnet 3.5 v2 (44). It leads on capability, price, inputs & features and context window. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Claude Sonnet 3.5 v2 or Grok 4.20 (Reasoning)?
Grok 4.20 (Reasoning) is cheaper at $1.25 input / $2.50 output per million tokens (official xAI API price). Claude Sonnet 3.5 v2 costs $3.00 input / $15.00 output per million tokens (median across 1 API provider). 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 $6.00 for Claude Sonnet 3.5 v2 (3.8× 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) and Claude Sonnet 3.5 v2 133.5 (#119 of 148). Their confidence ranges do not overlap (149.3–154.4 vs 129.2–137.5), so the gap is a real one. On individual benchmarks: GPQA Diamond — Grok 4.20 (Reasoning) 89.3%, Claude Sonnet 3.5 v2 55.3%; OTIS Mock AIME 2024–2025 — Grok 4.20 (Reasoning) 92.2%, Claude Sonnet 3.5 v2 8.5%.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 3.5 v2 and 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. Both 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 200,000 for Claude Sonnet 3.5 v2. Maximum output per response: Claude Sonnet 3.5 v2 up to 8,192, Grok 4.20 (Reasoning) up to 30,000 tokens.
Which can read images, PDFs, audio or video?
Claude Sonnet 3.5 v2 accepts text, images and PDFs; Grok 4.20 (Reasoning) accepts text, images and PDFs. They handle the same number of input types.
Are any of these open source?
No. Claude Sonnet 3.5 v2 and Grok 4.20 (Reasoning) are proprietary and only available through APIs and apps.
Which is newer?
Grok 4.20 (Reasoning) is the newest, released Mar 9, 2026. Claude Sonnet 3.5 v2 came out Oct 22, 2024. Knowledge cutoff: Claude Sonnet 3.5 v2 Apr 30, 2024.
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.
Related comparisons
- Add Gemini 2.0 FlashThree-way comparison
- Claude Sonnet 3.5 v2 vs Gemini 2.0 FlashGoogle · ECI 134.7
- Claude Sonnet 3.5 v2 vs GPT-4.1OpenAI · ECI 136.8
- Claude Sonnet 3.5 v2 vs Mistral Large 2.1Mistral AI · ECI 128.5
- Claude Sonnet 3.5 v2 vs Qwen2.5 72B InstructAlibaba (Qwen) · ECI 129.0
- Grok 4.20 (Reasoning) vs Kimi K2.6Moonshot AI · ECI 151.1
- Grok 4.20 (Reasoning) vs Gemini 3 Flash PreviewGoogle · ECI 151.8
