Art of Animation is for all intents and purposes different from Pop Century given its large number of suite offerings for larger families.
Pop Century is more popular than the All Stars and therefore can get away with a higher room rate.
The Skyliner gondola station for PC and AoA is halfway between those two resorts so as to serve them equally.
I am led to believe that there will be a bus loop at Caribbean Beach that connects the various sections, the front desk/restaurant, and the Skyliner station. This might be served by a separate "internal bus" or by Magic Kingdom and Animal Kingdom buses, or a combination of these.