Rotating weight is really great, as long as you are riding at a steady rate on a flat road, or downhill. But the heavier the rotating mass is, the more energy is expended to increase speed, regardless of how fast you are going. In most real world applications you're not riding along at exactly the same speed.
And when the world tilts up, you start paying to maintain that speed.
Commenting w/o thinking here, but I think that this is not true. When you're going up a hill, gravity is going to be applying an similar ******ing force, irrespective of where the mass of your wheels is concentrated. So, a rider will not suffer any more to maintain speed--on a bike of the same weight--by having rim-heavy wheels. Wheel weighting should have an effect on the speed curve though, and if a rider with rim-heavy wheels decided to just coast up the hill, you'd see his speed drop off very slowly at first, then quite rapidly (the opposite of accelerating up to speed). More uniformly weighted wheels would decellerate more...well, uniformtly
Both bikes should both coast to a stop a the same point...uh, I think
