These are my two favorite value resorts and I have stayed at both of them four times each.
I have found the bus service to be equal, Pop does have its own busses but its a much larger resort on its own than any of the All Stars.
I prefer the food a bit at Pop's food court but hate the way the gift shop is connected to it, it makes it that much more crowded in my opinion.
Pop now has more recently redone rooms with flat screen tv's and all Pop rooms have the privacy curtains. Only rooms in the preferred buildings at Music (Calypso section) and one section of standard (Jazz Inn) have those curtains. Pop also has the lake which I think is nice and its more centrally located.
Music has daily games by the pool and nightly movies. I also enjoy having Sports and Movies right next door, its sort of like having three resorts in one to enjoy.
I don't think you can make a bad choice, I would tend to lean towards Pop right now since its so recently rennovated however, Music has always been great for us.
I do think Music has the prettiest grounds, I enjoy the little fountain area. One thing to be aware of, Music is laid out differently than Pop. Whereas the Pop is laid out with the buidings sort of situated in circle, Music buildings are lined up one right after the other. Country Fair is the back section and a further walk to the food court than any section at Pop is.