Verdict
Built from the measurements below
- Accuracy is too close to call: Grok 4.7 scored 80.0% and Muse Spark Open 77.5% on the same 80 questions, a gap within what chance alone could produce.
- Muse Spark Open is 5.5× cheaper per question as billed ($0.0045 vs $0.025), reasoning tokens included.
- Muse Spark Open generates text 2.9× faster: 220 tokens per second against 77.
- Muse Spark Open starts answering sooner: 0.5 s to the first token, against 1.9 s for Grok 4.7.
- Muse Spark Open accepts more context: 1M tokens against 500k.
Which should you choose?
Choose Muse Spark Open for the lower cost per correct answer ($0.0058 against $0.031), faster streaming, a quicker first token, shorter outputs (about 964 tokens per question against 3,952), open weights you can run yourself, a 1M-token context window and more hosts to choose from on OpenRouter (6 against 1). The widest subject gap is in science: Grok 4.7 answered 27 of 30 correctly, Muse Spark Open 25 of 30. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.
Accuracy gap +2.5 points (z = 0.39). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.