Originally Posted by Pedaleur

Drag goes like frontal area, which is (in a perfect world) proportional to height squared.

Muscle power goes like body mass, which is proportional to height cubed, again all else neglected.

There are a huge number of variables (muscle vs. fat, positioning, etc.), all of which are hugely important, but from a fundamental physics point of view, a larger rider will have a higher power to drag ratio.

EDIT: "All else neglected" with respect to muscle power would mean that the proportions of all the body parts would be the same. In fact, this isn't likely true, but power probably increases at a rate greater than height squared. In fact, since lighter riders typically have higher power/weight ratios, it must be less than height cubed.