MiMo-V2.5-Pro-UltraSpeed vs Seed 2.1 Pro vs Step 5 Preview
Step 5 Preview comes out ahead, 57 to 50 and 43 on our weighted score, and it is the cheaper option too.
XiaomiMiMo-V2.5-Pro-UltraSpeed
43/100- ECI—
- Price$1.30 / $2.61
- Context1.05M
ByteDance SeedSeed 2.1 Pro
50/100- ECI—
- Price$0.891 / $4.45
- Context256K
- Our pick
StepFunStep 5 Preview
57/100- ECI—
- Price$1.00 / $2.70
- Context1M
Step 5 Preview is our pick
Step 5 Preview is the better all-round choice, scoring 57/100 against Seed 2.1 Pro (50) and MiMo-V2.5-Pro-UltraSpeed (43). It leads on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceStep 5 PreviewStep 5 Preview $1.43 · MiMo-V2.5-Pro-UltraSpeed $1.63 · Seed 2.1 Pro $1.78 per 1M tokens (3:1 blend)
- Longest contextMiMo-V2.5-Pro-UltraSpeedMiMo-V2.5-Pro-UltraSpeed 1,048,576 · Step 5 Preview 1,000,000 · Seed 2.1 Pro 256,000 tokens
- Widest inputsSeed 2.1 Pro and Step 5 PreviewMiMo-V2.5-Pro-UltraSpeed: Text · Seed 2.1 Pro: Text, Images, Video · Step 5 Preview: Text, Images, Video
- Self-hostingMiMo-V2.5-Pro-UltraSpeedPublishes downloadable weights
| Measure | Weight | MiMo-V2.5-Pro-UltraSpeed | Seed 2.1 Pro | Step 5 Preview |
|---|---|---|---|---|
| Price | 50% | 40 | 38 | 43 |
| Inputs & features | 30% | 35 | 80 | 80 |
| Context window | 20% | 61 | 36 | 60 |
| Overall | 100% | 43/100 | 50/100 | 57/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | MiMo-V2.5-Pro-UltraSpeedXiaomi | Seed 2.1 ProByteDance Seed | Step 5 PreviewStepFun |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $1.30 | $0.891 (best) | $1.00 |
| Output | $2.61 (best) | $4.45 | $2.70 |
| Cached input | $0.011 (best) | $0.178 | $0.05 |
| Blended (3:1) | $1.63 | $1.78 | $1.43 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official Xiaomi API | Official Volcengine Ark API | Official StepFun (Global) API |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 256,000 tokens | 1,000,000 tokens |
| Max output | 131,072 tokens | 256,000 tokens | 1,000,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | No | Yes | Yes |
| PDFs | No | No | No |
| Audio | No | No | No |
| Video | No | Yes | Yes |
| Reasoning | Yes | Yesminimal · low · medium · high · xhigh · max | Yeslow · medium · high |
| Tool calling | Yes | Yes | Yes |
| Structured output | No | Yes | Yes |
| Availability | |||
| Weights | Open | Proprietary | Proprietary |
| API model ID | mimo-v2.5-pro-ultraspeed | doubao-seed-2-1-pro-260628 | step-5-preview |
| API providers | 1 | 2 | 7 (best) |
| Released | Jun 8, 2026 | Jun 23, 2026 | Sep 16, 2026 |
| Knowledge cutoff | Dec 2024 | — | — |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- MiMo-V2.5-Pro-UltraSpeed$18.27
- Seed 2.1 Pro$17.81
- Step 5 Preview$15.40
Which should you choose?
Which is better: MiMo-V2.5-Pro-UltraSpeed, Seed 2.1 Pro or Step 5 Preview?
Step 5 Preview is the better all-round choice, scoring 57/100 against Seed 2.1 Pro (50) and MiMo-V2.5-Pro-UltraSpeed (43). It leads on price. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, MiMo-V2.5-Pro-UltraSpeed, Seed 2.1 Pro or Step 5 Preview?
Step 5 Preview is cheaper at $1.00 input / $2.70 output per million tokens (official StepFun (Global) API price). MiMo-V2.5-Pro-UltraSpeed costs $1.30 input / $2.61 output per million tokens (official Xiaomi API price); Seed 2.1 Pro costs $0.891 input / $4.45 output per million tokens (official Volcengine Ark API price). At a typical mix of three input tokens to one output token, that is $1.43 per million tokens for Step 5 Preview versus $1.63 for MiMo-V2.5-Pro-UltraSpeed (1.1× as much) and $1.78 for Seed 2.1 Pro (1.2× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. MiMo-V2.5-Pro-UltraSpeed has not been scored yet, Seed 2.1 Pro has not been scored yet and Step 5 Preview has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for MiMo-V2.5-Pro-UltraSpeed, Seed 2.1 Pro and Step 5 Preview yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. All three support tool calling for agent workflows.
Which has the bigger context window?
MiMo-V2.5-Pro-UltraSpeed has the largest context window at 1,048,576 tokens, against 1,000,000 for Step 5 Preview and 256,000 for Seed 2.1 Pro. Maximum output per response: MiMo-V2.5-Pro-UltraSpeed up to 131,072, Seed 2.1 Pro up to 256,000, Step 5 Preview up to 1,000,000 tokens.
Which can read images, PDFs, audio or video?
MiMo-V2.5-Pro-UltraSpeed accepts text; Seed 2.1 Pro accepts text, images and video; Step 5 Preview accepts text, images and video. Seed 2.1 Pro handles the widest range of inputs.
Are any of these open source?
MiMo-V2.5-Pro-UltraSpeed publishes its weights and can be self-hosted; Seed 2.1 Pro and Step 5 Preview is proprietary.
Which is newer?
Step 5 Preview is the newest, released Sep 16, 2026. Seed 2.1 Pro came out Jun 23, 2026; MiMo-V2.5-Pro-UltraSpeed came out Jun 8, 2026. Knowledge cutoff: MiMo-V2.5-Pro-UltraSpeed Dec 2024.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
