We've stayed at all the All-Stars, and Music has been the best for a couple reasons:
Middle resort means that when buses are shared, you don't end up missing a bus like I infrequently see happen with Movies. I don't have hard proof, but in my stays, Sports seems to have more tweens and teens, and while I've never seen bad behavior, they tend to be naturally noisier.
Any time that the buses would be more crowded (morning, and at park close) we've always had our own bus, so I would not let that scare you off.
We've got a 9 night stay at POP for the first time this August, and from what I've read, it should be just about the same as the All-Stars, which would be great.