Pushing Back on 'Just Use the Bigger Model'

Your model is underperforming on a domain-specific extraction task (pulling structured fields out of contracts). Leadership's proposed fix: "swap the 8B model we're using for the 70B version of the same model family — bigger models are better, this should just work."

1. Is parameter count alone a good predictor of whether this fixes the problem? Explain what it does and doesn't tell you.
2. What two or three questions would you actually want answered before recommending for or against the swap?
3. Give a concrete alternative explanation for the underperformance that a bigger model wouldn't fix, and how you'd distinguish it from "the model is just too small for this task."