Model Comparison
Solar Pro 2 (Preview) (Reasoning)
vs. Step 3.5 Flash
Comparing 2 AI models · 11 benchmarks · Upstage, StepFun
Recommended Pick
StStep 3.5 Flash5 metric winsStrongest on: Throughput, Intelligence, GPQA
Lowest Price
Solar Pro 2 (Preview) (Reasoning)
$0.00/1M input price
Best Reasoning
Solar Pro 2 (Preview) (Reasoning)
46.5 reasoning score
Blends available reasoning benchmarks
Composite Indices
Higher is better; speed and price are normalized
Standard Benchmarks
Only benchmarks with data are shown
Differences That Matter
Price gap
Solar Pro 2 (Preview) (Reasoning) is ∞x cheaper on input tokens than Step 3.5 Flash.
Reasoning gap
Solar Pro 2 (Preview) (Reasoning) leads Step 3.5 Flash by 3.9 points on reasoning.
Top-pick rationale
Step 3.5 Flash wins 5 measurable categories, including Throughput, Intelligence, GPQA, HLE.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
Solar Pro 2 (Preview) (Reasoning)
Upstage
TTFT
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Time
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tok/s
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Tokens
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Cost
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Step 3.5 Flash
StepFun
TTFT
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Time
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tok/s
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Tokens
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Cost
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Which answer was more useful?
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Full Comparison
| Metric | Up Solar Pro 2 (Preview) (Reasoning) | Top Pick St Step 3.5 Flash |
|---|---|---|
| Pricing per 1M tokens | ||
| Input Cost | $0.00/1M | $0.10/1M |
| Output Cost | $0.00/1M | $0.30/1M |
| Blended (3:1) | — | $0.15/1M |
| Specifications | ||
| Organization | Upstage | StepFun |
| Release Date | May 20, 2025 | Feb 2, 2026 |
| Performance & Speed | ||
| Throughput | — | 198.0 tok/s |
| TTFT | — | 811ms |
| Latency | — | 10913ms |
| Composite Indices | ||
| Value Score | — | 100.0 |
| Reasoning Score | 46.5 | 42.6 |
| Intelligence | 12.5 | 25.5 |
| Standard Benchmarks | ||
| GPQA | 57.8% | 83.1% |
| MMLU Pro | 76.8% | — |
| HLE | 5.7% | 19.1% |
| LiveCodeBench | 46.2% | — |
| MATH 500 | 90.0% | — |
| AIME (Original) | 66.3% | — |
| SciCode | 16.4% | 40.4% |
| LCR | — | 43.0% |
| IFBench | — | 64.6% |
| TAU-bench v2 | — | 94.4% |
| TerminalBench Hard | — | 27.3% |
Key Takeaways
Solar Pro 2 (Preview) (Reasoning) offers the best value at $0.00/1M,making it ideal for high-volume applications and cost-conscious projects.
Solar Pro 2 (Preview) (Reasoning) has the strongest reasoning profile with a 46.5 reasoning score,combining the available reasoning-heavy benchmarks.
All models support context windows of ∞+ tokens,suitable for processing lengthy documents and maintaining extended conversations.
When to Choose Each Model
Solar Pro 2 (Preview) (Reasoning)
- Cost-sensitive applications
- High-volume processing
- Complex reasoning tasks
- Research & analysis
Step 3.5 Flash
- General-purpose AI
- Versatile applications
