StepFun Step 3.5 Flash vs ChatGPT
Which one should you pick? Here's the full breakdown.
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
ChatGPT
The chatbot that started the AI revolution -- most popular AI assistant in the world
| Category | StepFun Step 3.5 Flash | ChatGPT |
|---|---|---|
| Ease of Use | 6.0 | 10.0 |
| Output Quality | 8.0 | 8.0 |
| Value | 9.0 | 8.0 |
| Features | 8.0 | 9.0 |
| Overall | 7.8 | 8.8 |
Pricing Comparison
| Feature | StepFun Step 3.5 Flash | ChatGPT |
|---|---|---|
| Free Tier | Yes | Yes |
| Starting Price | $0 | $0 |
Benchmark Head-to-Head
GPT-5.4 benchmarks — StepFun Step 3.5 Flash has no published benchmarks
| Benchmark | Description | Score |
|---|---|---|
| MMLU | Knowledge across 57 subjects | 91% |
| GPQA Diamond | Graduate-level science questions | 92.8% |
| AIME 2024 | Competition math problems | 83.3% |
| HumanEval | Python code generation | 95% |
| SWE-bench | Real GitHub issue fixing | 72% |
| ARC-AGI | Abstract reasoning puzzles | 73.3% |
Which Should You Pick?
Pick StepFun Step 3.5 Flash if...
- ✓Better value for money (9/10)
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 FlashPick ChatGPT if...
- ✓Easier to use (10 vs 6)
- ✓More features (9 vs 8)
Everyone. Seriously -- if you're new to AI or want the most complete all-in-one package, ChatGPT is the default recommendation.
Visit ChatGPTOur Verdict
ChatGPT is the clear winner here with 8.8/10 vs 7.8/10. StepFun Step 3.5 Flash isn't bad, but ChatGPT outperforms it across the board. Pick StepFun Step 3.5 Flash only if 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.