DeepSeek vs StepFun Step 3.5 Flash
Which one should you pick? Here's the full breakdown.
DeepSeek
Near-frontier reasoning for pennies on the dollar -- the open-source LLM that made Silicon Valley nervous
StepFun Step 3.5 Flash
StepFun's (China) agent-focused open-weight model -- Step 3.5 Flash launched 2026-02-01. 196B sparse MoE, ~11B active. Benchmarks slightly ahead of DeepSeek V3.2 at over 3x smaller total size. Step 3 (321B / 38B active, Apache 2.0) and Step3-VL-10B multimodal also in the family
| Category | DeepSeek | StepFun Step 3.5 Flash |
|---|---|---|
| Ease of Use | 7.5 | 6.0 |
| Output Quality | 8.0 | 8.0 |
| Value | 9.5 | 9.0 |
| Features | 7.0 | 8.0 |
| Overall | 8.0 | 7.8 |
Pricing Comparison
| Feature | DeepSeek | StepFun Step 3.5 Flash |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Benchmark Head-to-Head
DeepSeek V3.2 benchmarks — StepFun Step 3.5 Flash has no published benchmarks
| Benchmark | Description | Score |
|---|---|---|
| MMLU | Knowledge across 57 subjects | 90.8% |
| MMLU-Pro | Harder multi-subject reasoning | 85% |
| GPQA Diamond | Graduate-level science questions | 79.9% |
| HumanEval | Python code generation | 91.5% |
| SWE-bench | Real GitHub issue fixing | 67.8% |
Which Should You Pick?
Pick DeepSeek if...
- ✓Easier to use (7.5 vs 6)
Developers and teams who need strong reasoning and coding capabilities on a budget. If you're building AI features and can't justify GPT-4 API costs, DeepSeek is the obvious first stop.
Visit DeepSeekPick StepFun Step 3.5 Flash if...
- ✓More features (8 vs 7)
Teams building agent systems on Chinese open-weight foundations who want something other than DeepSeek or Qwen, especially if agentic tool-use is the primary workload. Also good for Chinese-market products where StepFun's domestic tuning advantages matter. And for anyone looking to add diversity to their open-weight evaluation matrix beyond the top-3 Chinese labs.
Visit StepFun Step 3.5 FlashOur Verdict
DeepSeek and StepFun Step 3.5 Flash are extremely close overall. Your choice comes down to specific needs -- DeepSeek is better for developers and teams who need strong reasoning and coding capabilities on a budget, while StepFun Step 3.5 Flash works best for teams building agent systems on chinese open-weight foundations who want something other than deepseek or qwen, especially if agentic tool-use is the primary workload.