The All Stars are very similar to each other except w/ different theming. I like them all!
Pop has a better food court (love the grilled flatbreads) and a lovely walk around the lake--but it also has 1,000 more rooms. I find the chaos and noise at the food court overwhelming at times and I dislike "having" to walk through the gift shop to get to the food court.
I've stayed at each value multiple times (except AoA where once was enough). ASMusic is my favorite for theming and it seems a bit more quiet than the others.
Bus service at WDW can be ANYTHING at ANY TIME for ANY resort. I think the bus sharing at All Stars is WAY overstated. I stay at the AS at least 2-3 times per year and I would guess that we share buses 25% of the time or less. Even when we do, I see no difference in that and a moderate with multiple stops within the resort.
The pools are all basically the same--one main pool and 1-2 smaller "quiet" pools. None have slides or deep ends.