Which model, and why

The wrong question is "how important is this task?" — everything feels important. The right question is about the shape of the work.

The decisive test: is there a cheap verifier downstream?

If a mistake in this output would be caught mechanically — by a compiler, a test, a schema, a deterministic checker, a later verification pass — a cheaper model is usually correct. The verifier is the quality control; the generator only has to get close. Wasting a frontier model on work that is checked for free buys nothing.

If this output IS the last line of defence — nothing downstream can tell whether it is wrong — spend the strong model. When the model is the verifier, its judgement is the product.

Everything below follows from that one test.

Spend the most capable model on