We LOVE Pop! We walked through AoA during our last stay and both said if we had little ones AoA would be the way to go due to the theming. Little kids would be highly amused by all the larger than life sea life that is surrounding the pool area. I’ve never seen the rooms so I can’t comment on.
Pop is a great resort for older kids.
And the skyliner…it’s the BEST resort transportation and serves both AoA and Pop. I think the walk to the skyliner is relatively the same distance from whatever resort you’re coming from. Both resorts share the same skyliner hub.
I'd only select based on type of room needed. Obviously AoA if wanting one of the suites but if a regular room then I'd for sure do Pop preferred over Little Mermaid, and I'd likely do Pop standard over Little Mermaid as well. Can walk over to AoA to check out the resort. Pop main buildings are accessible from the other, about a 7 minute walk between.