Pick a winner in each dimension — change your vote anytime.
Pricing and capabilities synced from the OpenRouter catalogue. Scores are editorial (0–10).
Choose DeepSeek V4 Flash if you want cheap, high-volume open-weight agent steps. Choose GPT-5.5 if you want hard reasoning and coding for teams in the OpenAI ecosystem.
In our editorial scoring, GPT-5.5 leads in 3 of five dimensions (output quality, agentic ability and reliability), while DeepSeek V4 Flash leads in 2. On price, DeepSeek V4 Flash runs about $0.12 per 1M tokens (blended) and is open-weight; GPT-5.5 is about $13 and proprietary.
The model picks the moves; the agent runs the loop, the tools, and the guardrails. Once you've chosen a model, see which agent gets the most out of it.