Pabelson, if you think that the whole thing boils down to speed accuracy and rumble, you are sadly mistaken. Internal resonance within the drive system and resistance to external vibration and the period and frequency of those vibrations are just three more of the various factors that come into play.
I'm not talking about "the whole thing"; I'm talking only about factors for which one drive system or the other has an obvious theoretical advantage. So if you want to convince me that I'm mistaken (and I might be--I certainly can't claim any real technical expertise here), then the first thing you have to do is offer a plausible reason why one drive system would be presumptively better than the other for each of the three factors you mentioned.
Even if the factors you mention are relevant to the belt/DD question, I suspect the speed accuracy/rumble tradeoff is still the dominant factor. If one drive system could be shown to be superior in minimizing both speed inaccuracy and rumble, I supect this debate would be over. I seriously doubt the factors you mentioned could tip the scales in the other direction.