GPT-5.6 Terra vs GPT-6.1 Sol: accuracy, speed and price

• Accuracy is too close to call: GPT-5.6 Terra scored 75.0% and GPT-6.1 Sol 76.2% on the same 80 questions, a gap within what chance alone could produce.
• GPT-6.1 Sol is 2.2× cheaper per question as billed ($0.0029 vs $0.0063), reasoning tokens included.
• GPT-5.6 Terra generates text 2.4× faster: 101 tokens per second against 41.
• GPT-5.6 Terra starts answering sooner: 1.1 s to the first token, against 2.1 s for GPT-6.1 Sol.

Which should you choose?

Choose GPT-5.6 Terra for faster streaming and a quicker first token. Choose GPT-6.1 Sol for the lower cost per correct answer ($0.0037 against $0.0084) and shorter outputs (about 224 tokens per question against 472).

Accuracy gap -1.2 points (z = -0.18). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.