DeepSeek V4 Flash vs GPT-5.5 Instant
Pricing, benchmarks, and use case comparison
Quick take
- •DeepSeek V4 Flash is meaningfully stronger at cost efficiency (95 vs 70 on our capability index).
- •GPT-5.5 Instant is meaningfully stronger at multimodal (82 vs 10).
- •DeepSeek V4 Flash is open-weights (free to self-host); GPT-5.5 Instant is paid API only.
Specs comparison
| DeepSeek V4 Flash | GPT-5.5 Instant | |
|---|---|---|
| Provider | DeepSeek | OpenAI |
| Type | Open source | Closed source |
| Context window | 1M tokens | ✓1050000 |
| Input / 1M tokens | ✓Free (self-host) | 5.00 |
| Output / 1M tokens | Free (self-host) | 30.00 |
| Release date | 2026-04 | 2026-05 |
Benchmarks
| Benchmark | DeepSeek V4 Flash | GPT-5.5 Instant |
|---|---|---|
| Reasoning (vs V4 Pro) | Closely approaches V4 Pro | - |
| AIME 2025 | - | 81.2 |
| Terminal-Bench 2.0 | - | 82.7 |
| FrontierMath Tier 1–3 | - | 51.7 |
Scores sourced from official provider release posts and independent benchmark aggregators.
Which should you choose?
Choose DeepSeek V4 Flash if...
- →You want most of V4 Pro's capability at a lower price and higher throughput
- →You need long context but on a tighter compute or cost budget
- →You are serving high request volumes where per-token cost dominates
- →You want an open model small enough to self-host on modest multi-GPU setups
Choose GPT-5.5 Instant if...
- →Interactive chat and everyday assistant tasks where responsiveness matters most
- →High-volume, latency-sensitive workloads that do not need deep reasoning
- →General questions, drafting, and summarization at speed