This may or may not be true--I have a nagging suspicion that a bike wheel (in terms of physics) is more than a simple disk. There may be some harmonics involved in the spokes or the way the wheel flexes may make hub-centering the mass more deisreable--I just don't know. Gyroscopically speaking, a wheel weighted more toward the rim will be harder to rotate perpendicular to the plane ot its rotation--so, if one's pedaling style involves a lot of tiny movements in the front wheel, or a swinging of the bike, I can see how a rim-weighted wheel might be more exhausting/inefficient. Nevertheless, I'm taking a very simplistic approach and I admit it

One thing I DO know for a fact is that low-spoke-count wheels mean that you're SOL if you break a spoke in the middle of nowhere