I have to agree and disagree with some of you...
First of all, the theming at Universal has nothing on the ones at Disney. The attention to detail is good, but if you look around you can find a soundstage or a staff-only area (at IOA, at Universal that's acceptable I guess) Not to say that it isn't good, but it's not totally immersive because you can sometimes see behind-the-scenes.
I do love the seclusion you feel when staying onsite. Everytime I'm there at the hotel I feel like nothing matters except me having fun, and that feeling is just amazing. You could tell me I'm miles behind in paperwork and I wouldn't even care because being at the resort is like some kind of drug. That ultimate relaxation that's there is great, but what I also love is that if the park opens at 9 in the morning and you want to be there at rope-drop, you don't have to worry about taking a bus and a boat and a taxi and a monorail--you can just walk over, ride a bike over, ride a boat over (and what's better, being there for opening isn't even a neccesity because the hotel guests get to skip the lines!)
Another thing I like is hte fact that even if you're just going for a day, you can easily do both parks. You just WALK. If you want to eat at Bubba Gump or Nascar Cafe for lunch, you just do it. At Disney, you're limited to one park (unless you want to spend nearly an hour transporting to the next one) and its food (Downtown Disney, for some odd reason, isn't close to anything except Typhoon Lagoon
)
There you have it; I guess Universal is more desirable as an ultimate vacation destination.