Write a professional email, and tasks like it, ranked by this site's own recorded cost, speed, and accuracy, blended equally. Not one hand-picked answer: the top 3, and why each one placed where it did.
GPT-5.6 Luna is the best overall blend of cost, speed, and accuracy for this task: 90% accurate, 1.7 s to run, $0.0002.
GPT-5.6 Terra is close behind — the fastest of the three here: 93% accurate, 1.9 s to run, $0.0012.
GPT-5.6 Sol is close behind — the fastest of the three here: 93% accurate, 2.0 s to run, $0.0013.
These get talked about a lot for this category, but we haven’t run them through our own tests yet, so we won’t rank them next to a model we’ve actually measured. Worth knowing exists, not a recommendation.
Every pick above is backed by this site’s own recorded runs against the live Anthropic, OpenAI, Meta, DeepSeek, Google, Z-AI, NVIDIA, and MiniMax APIs; never a marketing number. How we measure → · Full model comparison → · New models →