5W is less than 1% for a given effort. Probably less than 0.5%. As someone noted before during a similar discussion, that's within a standard margin of error. So, I imagine that for scientific purposes, they could all be considered identical. And the differentiating factors being other things than aerodynamics (e.g. stiffness, tire options, price, aesthetics).
I'm sure that between a $1,000 wheel and a $4,000 wheel, one could probably buy the $1,000 wheel and use that extra $3,000 to find more than 5W somewhere else
