Model Comparison
Sonar Pro
vs. Step 3.5 Flash
Comparing 2 AI models · 11 benchmarks · Perplexity, StepFun
Recommended Pick
StStep 3.5 Flash6 metric winsStrongest on: Throughput, Reasoning, Intelligence
Lowest Price
Sonar Pro
$0.00/1M input price
Best Reasoning
Step 3.5 Flash
42.6 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
Sonar Pro is ∞x cheaper on input tokens than Step 3.5 Flash.
Reasoning gap
Step 3.5 Flash leads Sonar Pro by 6.9 points on reasoning.
Top-pick rationale
Step 3.5 Flash wins 6 measurable categories, including Throughput, Reasoning, Intelligence, GPQA.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
Sonar Pro
Perplexity
TTFT
—
Time
—
tok/s
—
Tokens
—
Cost
—
Step 3.5 Flash
StepFun
TTFT
—
Time
—
tok/s
—
Tokens
—
Cost
—
Which answer was more useful?
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Full Comparison
| Metric | Pe Sonar Pro | 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 | Perplexity | StepFun |
| Release Date | Jan 21, 2025 | Feb 2, 2026 |
| Performance & Speed | ||
| Throughput | — | 202.4 tok/s |
| TTFT | — | 788ms |
| Latency | — | 10671ms |
| Composite Indices | ||
| Value Score | — | 100.0 |
| Reasoning Score | 35.7 | 42.6 |
| Intelligence | 9.3 | 25.5 |
| Standard Benchmarks | ||
| GPQA | 57.8% | 83.1% |
| MMLU Pro | 75.5% | — |
| HLE | 7.9% | 19.1% |
| LiveCodeBench | 27.5% | — |
| MATH 500 | 74.5% | — |
| AIME (Original) | 29.0% | — |
| SciCode | 22.6% | 40.4% |
| LCR | — | 43.0% |
| IFBench | — | 64.6% |
| TAU-bench v2 | — | 94.4% |
| TerminalBench Hard | — | 27.3% |
Key Takeaways
Sonar Pro offers the best value at $0.00/1M,making it ideal for high-volume applications and cost-conscious projects.
Step 3.5 Flash has the strongest reasoning profile with a 42.6 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
Sonar Pro
- Cost-sensitive applications
- High-volume processing
Step 3.5 Flash
- Complex reasoning tasks
- Research & analysis
