Model Comparison
o3-pro
vs. Step 3.5 Flash
Comparing 2 AI models · 7 benchmarks · OpenAI, StepFun
Recommended Pick
StStep 3.5 Flash7 metric winsStrongest on: Value, Input price, Output price
Best Value
Step 3.5 Flash
100.0 value score
42.6 reasoning / $0.15/1M
Lowest Price
Step 3.5 Flash
$0.10/1M input price
Best Reasoning
o3-pro
58.5 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
Best value
Step 3.5 Flash has the strongest quality-to-price mix at 100.0 out of 100 value points.
Price gap
Step 3.5 Flash is 200x cheaper on input tokens than o3-pro.
Speed gap
Step 3.5 Flash generates about 6.7x as many tokens per second as o3-pro.
Reasoning gap
o3-pro leads Step 3.5 Flash by 15.9 points on reasoning.
Top-pick rationale
Step 3.5 Flash wins 7 measurable categories, including Value, Input price, Output price, Blended price.
Response Face-Off
Run one prompt through the selected models and compare response quality with live speed and cost context.
o3-pro
OpenAI
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 | Op o3-pro | Top Pick St Step 3.5 Flash |
|---|---|---|
| Pricing per 1M tokens | ||
| Input Cost | $20.00/1M | $0.10/1M |
| Output Cost | $80.00/1M | $0.30/1M |
| Blended (3:1) | $35.00/1M | $0.15/1M |
| Specifications | ||
| Organization | OpenAI | StepFun |
| Release Date | Jun 10, 2025 | Feb 2, 2026 |
| Performance & Speed | ||
| Throughput | 31.3 tok/s | 208.6 tok/s |
| TTFT | 61632ms | 783ms |
| Latency | 61632ms | 10371ms |
| Composite Indices | ||
| Value Score | 0.6 | 100.0 |
| Reasoning Score | 58.5 | 42.6 |
| Intelligence | 32.5 | 25.5 |
| Standard Benchmarks | ||
| GPQA | 84.5% | 83.1% |
| HLE | — | 19.1% |
| SciCode | — | 40.4% |
| LCR | — | 43.0% |
| IFBench | — | 64.6% |
| TAU-bench v2 | — | 94.4% |
| TerminalBench Hard | — | 27.3% |
Key Takeaways
Step 3.5 Flash offers the best value at $0.10/1M,making it ideal for high-volume applications and cost-conscious projects.
o3-pro has the strongest reasoning profile with a 58.5 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
o3-pro
- Complex reasoning tasks
- Research & analysis
Step 3.5 Flash
- Cost-sensitive applications
- High-volume processing
