Verdict
Built from the measurements below
- Accuracy is too close to call: GPT-5.4 scored 72.5% and o3 72.5% on the same 80 questions, a gap within what chance alone could produce.
- o3 is 1.3× cheaper per question as billed ($0.0088 vs $0.011), reasoning tokens included.
- o3 generates text 3.0× faster: 163 tokens per second against 55.
- o3 starts answering sooner: 1.2 s to the first token, against 1.7 s for GPT-5.4.
- GPT-5.4 accepts more context: 1.1M tokens against 200k.
Which should you choose?
Choose GPT-5.4 for a 1.1M-token context window and more hosts to choose from on OpenRouter (3 against 1). Choose o3 for the lower cost per correct answer ($0.012 against $0.016), faster streaming and a quicker first token. The widest subject gap is in medicine: o3 answered 7 of 11 correctly, GPT-5.4 4 of 11. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.
Accuracy gap +0.0 points (z = 0.00). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.