Verdict
Built from the measurements below
- Accuracy is too close to call: Claude Sonnet 5.5 scored 78.8% and Gemini 4 Argon 84.8% on the same 80 questions, a gap within what chance alone could produce.
- Claude Sonnet 5.5 is 1.2× cheaper per question as billed ($0.0054 vs $0.0063), reasoning tokens included.
- Claude Sonnet 5.5 generates text 1.8× faster: 126 tokens per second against 69.
- Claude Sonnet 5.5 starts answering sooner: 0.7 s to the first token, against 3.3 s for Gemini 4 Argon.
Which should you choose?
Choose Claude Sonnet 5.5 for faster streaming, a quicker first token and more hosts to choose from on OpenRouter (5 against 2). The widest subject gap is in law: Gemini 4 Argon answered 6 of 6 correctly, Claude Sonnet 5.5 3 of 6. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.
Accuracy gap -6.1 points (z = -0.99). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.