Verdict
Built from the measurements below
- Accuracy is too close to call: GPT-5.3-Codex scored 82.5% and Grok 4.7 80.0% on the same 80 questions, a gap within what chance alone could produce.
- GPT-5.3-Codex is 2.4× cheaper per question as billed ($0.01 vs $0.025), reasoning tokens included.
- GPT-5.3-Codex generates text 1.2× faster: 95 tokens per second against 77.
- GPT-5.3-Codex starts answering sooner: 1.4 s to the first token, against 1.9 s for Grok 4.7.
- Grok 4.7 accepts more context: 500k tokens against 400k.
Which should you choose?
Choose GPT-5.3-Codex for the lower cost per correct answer ($0.013 against $0.031), faster streaming, a quicker first token and shorter outputs (about 699 tokens per question against 3,952). Choose Grok 4.7 for a 500k-token context window.
Accuracy gap +2.5 points (z = 0.41). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.