Verdict
Built from the measurements below
- Accuracy is too close to call: Gemini 3.1 Pro Preview scored 77.5% and Muse Spark Open 77.5% on the same 80 questions, a gap within what chance alone could produce.
- Muse Spark Open is 3.8× cheaper per question as billed ($0.0045 vs $0.017), reasoning tokens included.
- Muse Spark Open generates text 1.8× faster: 220 tokens per second against 124.
- Muse Spark Open starts answering sooner: 0.5 s to the first token, against 3.4 s for Gemini 3.1 Pro Preview.
Which should you choose?
Choose Muse Spark Open for the lower cost per correct answer ($0.0058 against $0.022), faster streaming, a quicker first token, open weights you can run yourself and more hosts to choose from on OpenRouter (6 against 2).
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.