Pop Century is definately better than the All-Star resorts. Pop Century is the newest of the values. All three of the All-Star resorts share the same buses while Pop Century has its own. Also, Pop Century is a little cheaper (with tax) because it's in a different county.
It's not my favorite Disney resort, but it's very nice for the money. We are staying there when we go to Disney in March.
If you have any specific questions about the resort, let me know and I'll help you if I can.
ETA: If you are booking a package (room + tickets) you should be able to get free water park and park hopping with code APV.