I've only been to Cancun, but here's my arguement:
Everywhere cool costs fifty cents to go to. Just grab a bus, give the guy money and you're there in under 15 minutes. All the places are on one long-ass strip. Then, when you get there, you usually pay a cover charge, and it's open bar, such as Bulldog Cafe, LaBoom, and Coco Bongo club. Senor Frog's and places like that are cool, but you gotta pay by the drink which gets pricey, especially when you're so drunk, you have trouble converting peso's to dollars. The mexican's are known for screwing american's like that.