Hi Allison, thanks so much for bringing your question to the Disney Parks Moms Panel. On our last vacation to Disney's All-Star Music we shared a bus between all the other All-Star Resorts. First the bus stops at All-Star Sports, then All-Star Music, and finally All-Star Movies. During peak travel times, the All-Star Resorts have their own buses that go directly to their respective resort. Disney's Pop Century Resort on the other hand has its own bus system, which could be a legitimate reason for you to choose to stay there.
We enjoyed staying at All-Star Music because it was right in the middle of the other two All-Star resorts. We got a chance to eat at each of the food courts and roam the properties to look at all of the cool larger than life icons. My son's favorite was 'Andy's Room' at All-Star Movies, and he begged me to stay there during our next vacation.
Although I have never personally stayed at Pop Century, I opened up a conversation with some of my fellow Moms Panelists to get their opinions on the resort. Heather, Rachel, Autumn, Andrea, and Kathy all prefer Pop Century to the All-Star Resorts. They each have their own reasons, and some even include the bus route as being a factor. They also mention that the proximity of Pop Century to Disney's Art of Animation Resort is a plus because you can go check out
Landscape of Flavors and enjoy all of the beautifully themed courtyards.
I hope this information helps your decision.
No matter where you choose to stay, I wish you all a magical fourth family vacation! Please feel free to stop by with more questions, we'd be happy to help.