Verdict
Built from the measurements below
- Accuracy is too close to call: GPT-6.1 Terra scored 73.8% and GPT-6 Sol 73.8% on the same 80 questions, a gap within what chance alone could produce.
- GPT-6.1 Terra is 1.8× cheaper per question as billed ($0.0013 vs $0.0024), reasoning tokens included.
- GPT-6.1 Terra generates text 1.3× faster: 122 tokens per second against 92.
- GPT-6 Sol starts answering sooner: 0.9 s to the first token, against 2.4 s for GPT-6.1 Terra.
Which should you choose?
Choose GPT-6.1 Terra for the lower cost per correct answer ($0.0017 against $0.0032) and faster streaming. Choose GPT-6 Sol for a quicker first token.
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.