Solar Pro 2 vs Grok 4.1 Fast
Grok 4.1 Fast comes out ahead, 71 to 52 on our weighted score, though Solar Pro 2 is 9% cheaper per token.
Upstage
Solar Pro 2
52/100- ECI—
- Price$0.25 / $0.25
- Context66K
- Our pick
xAIGrok 4.1 Fast
71/100- ECI—
- Price$0.20 / $0.50
- Context2M
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Make it a three-way comparison.
Grok 4.1 Fast is our pick
Grok 4.1 Fast is the better all-round choice, scoring 71/100 against Solar Pro 2 (52). It leads on inputs & features and context window. Solar Pro 2 wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceSolar Pro 2Solar Pro 2 $0.25 · Grok 4.1 Fast $0.275 per 1M tokens (3:1 blend)
- Longest contextGrok 4.1 FastGrok 4.1 Fast 2,000,000 · Solar Pro 2 65,536 tokens
- Widest inputsGrok 4.1 FastSolar Pro 2: Text · Grok 4.1 Fast: Text, Images
- Self-hostingNo open weightsBoth are available only through APIs
| Measure | Weight | Solar Pro 2 | Grok 4.1 Fast |
|---|---|---|---|
| Price | 50% | 78 | 76 |
| Inputs & features | 30% | 35 | 60 |
| Context window | 20% | 12 | 72 |
| Overall | 100% | 52/100 | 71/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Solar Pro 2Upstage | Grok 4.1 FastxAI |
|---|---|---|
| Capability | ||
| Capabilities Index (ECI) | — | — |
| ECI rank | — | — |
| Price per million tokens | ||
| Input | $0.25 | $0.20 (best) |
| Output | $0.25 (best) | $0.50 |
| Cached input | — | — |
| Blended (3:1) | $0.25 (best) | $0.275 |
| Long-context rate | Same rate | Same rate |
| Price source | Official Upstage API | Median of 2 providers |
| Limits | ||
| Context window | 65,536 tokens | 2,000,000 tokens (best) |
| Max output | 8,192 tokens | 30,000 tokens (best) |
| Inputs and features | ||
| Text | Yes | Yes |
| Images | No | Yes |
| PDFs | No | No |
| Audio | No | No |
| Video | No | No |
| Reasoning | Yesminimal · high | No |
| Tool calling | Yes | Yes |
| Structured output | No | Yes |
| Availability | ||
| Weights | Proprietary | Proprietary |
| API model ID | solar-pro2 | — |
| API providers | 2 | 2 |
| Released | May 20, 2025 | Nov 19, 2025 |
| Knowledge cutoff | Mar 2025 | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Solar Pro 2$3.00
- Grok 4.1 Fast$3.00
Which should you choose?
Which is better: Solar Pro 2 or Grok 4.1 Fast?
Grok 4.1 Fast is the better all-round choice, scoring 71/100 against Solar Pro 2 (52). It leads on inputs & features and context window. Solar Pro 2 wins on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, Solar Pro 2 or Grok 4.1 Fast?
Solar Pro 2 is cheaper at $0.25 input / $0.25 output per million tokens (official Upstage API price). Grok 4.1 Fast costs $0.20 input / $0.50 output per million tokens (median across 2 API providers). At a typical mix of three input tokens to one output token, that is $0.25 per million tokens for Solar Pro 2 versus $0.275 for Grok 4.1 Fast (1.1× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers both models yet. Solar Pro 2 has not been scored yet and Grok 4.1 Fast has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for Solar Pro 2 and Grok 4.1 Fast yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.
Which has the bigger context window?
Grok 4.1 Fast has the largest context window at 2,000,000 tokens, against 65,536 for Solar Pro 2. Maximum output per response: Solar Pro 2 up to 8,192, Grok 4.1 Fast up to 30,000 tokens.
Which can read images, PDFs, audio or video?
Solar Pro 2 accepts text; Grok 4.1 Fast accepts text and images. Grok 4.1 Fast handles the widest range of inputs.
Are any of these open source?
No. Solar Pro 2 and Grok 4.1 Fast are proprietary and only available through APIs and apps.
Which is newer?
Grok 4.1 Fast is the newest, released Nov 19, 2025. Solar Pro 2 came out May 20, 2025. Knowledge cutoff: Solar Pro 2 Mar 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.
