OpenAI: GPT-5.5 vs DeepSeek: DeepSeek V4 Flash 0423
As of 2026-10-19: On the un-leaked meo benchmark, OpenAI: GPT-5.5 is the more accurate of the two (94.1% vs 81.8%), while DeepSeek: DeepSeek V4 Flash 0423 is cheaper per correct answer. Compared on accuracy, Effective Value (π), cost, speed, context, and pricing β all from the un-leaked meo benchmark.
| Metric | OpenAI: GPT-5.5 | DeepSeek: DeepSeek V4 Flash 0423 |
|---|---|---|
| meo rank | #1 | #11 |
| Accuracy | 94.1% | 81.8% |
| π index (top=100) | 23.2 | 0.43 |
| $ / correct answer | $0.0336 | $0.0016 |
| Seconds / correct | 22 | 169 |
| Context window | 1.1M | 1.0M |
| Price out ($/M) | $30.00 | $0.18 |
| Open weights | β | Yes |
Green = the stronger value on that metric. π indexed to the leaderboard top = 100.
Frequently asked questions
Is OpenAI: GPT-5.5 better than DeepSeek: DeepSeek V4 Flash 0423?
On accuracy, OpenAI: GPT-5.5 leads (94.1% vs 81.8%). On Effective Value (π), which weights accuracy for deep agentic chains, OpenAI: GPT-5.5 is ahead. βBetterβ depends on whether you optimize for accuracy, cost, or speed.
Which is cheaper, OpenAI: GPT-5.5 or DeepSeek: DeepSeek V4 Flash 0423?
DeepSeek: DeepSeek V4 Flash 0423 costs less per correct answer ($0.0016 vs $0.0336), which already accounts for accuracy β a cheap-but-wrong model is penalized.
OpenAI: GPT-5.5 vs DeepSeek: DeepSeek V4 Flash 0423 for agentic / coding work?
For long multi-step chains, rank by Effective Value (π): OpenAI: GPT-5.5 leads here. Accuracy compounds across steps, so the more accurate model usually wins deep agentic work even if it is slower.
Full pages: OpenAI: GPT-5.5 (OpenAI) Β· DeepSeek: DeepSeek V4 Flash 0423 (DeepSeek). More: all comparisons Β· full leaderboard Β· methodology.