I liked both of them. Coronado is a moderate and Pop is a value resort. Disney lists the differences between the two resort categories pretty well on their website.
Having said that, I think the differences are things that most folks can probably live with.
If the theming of one interests you greatly over the other, then you should go with that resort. Like if you live in, or have ever lived in the Southwestern US, you might yearn for a southwest theme - or you might be opposed to a Disney version. Maybe you love or dislike Mexican food. Pop is more generic American. I can also say that Coronado in one of few places on property that HAS Mexican food, and it has the best Mexican food on property.
Coronado is also a convention resort. So if you stay there you may well see convention goers. I didn't mind it, but some folks dislike it. Sometimes the conveniotn goers do drink at the pool bar. Every Disney resort has a bar at their main pool, but the one at Coronado attacts more drinkers perhaps than other resorts. Also, the folks hanging out there may well be discussing their convention - and not so much which park they just came from.
Pop has better transportation though, IMO.
Both are large resorts.