I may be biased because I love both Fantasmics. I especially love that WDW built a stadium for it, so that my 5' 2" body doesn't have to try to stretch to see what's going on. At DL, there is no seating area (aside from the Dessert Buffet). You basically have to find space to sit on the ground, or stand. Personally, we come right before the show starts and just find a place to stand.
Fantasmic at DL is definitely different. As I said, I like both of them in different ways. I've heard quite a few people say that they think DL's is better.