Do you buy that much music between syncs? I plug my iPod to my Mac just about every day, at most I move over 1-2 podcasts and maybe 1-2 songs. And when I plug in the iPod, I usually use the computer for several minutes, and in that case even Bluetooth would be fast enough to sync that content over.
Using WiFi, 125MB would take about 25 seconds. How would that work? Well, I could start the computer, and start the sync. I would then start to head out the door, and by the time I close my front-door, the sync would be finished. With a cable, I would have to wait by the computer until the sync is finished.
And, at least Zune offers this feature, whereas iPod does not. Don't like wireless syncing? Then don't use it, and use the cable. That way there would be no real difference between the Zune and the iPod. As far as syncing goes, the Zune offers all the features iPod does, while offering something extra that iPod does not offer. Doesn't that mean that as far as syncing goes, Zune beats the iPod?
And it would be radically different if you used a cable? Why?