i went last year. we went to both universal for 3 days and disney world for the other 4 days. We got the passes that will let you go in all the different parks, thats the way to go. The universal pass will let you go into universal studios and their islands of adventure. disneys pass will let you go in all 4 of their parks.
Personally i liked disney MUCH better. (was 17 at the time) I wouldn't even recomend wasting your time with universal studios. its very over rated, packed with people, over priced and the rides suck. back to the future was cool, and so was walking down their streets and seeing the stuff but it wasnt' very entertaining. islands of adventure was a lot better. most of the rides are great; ride the hulk! that park is pretty fun. the thing i really don't like about it is their fast pass thing. you can only get 2-3 a day at universal, where as at disneyland you can get 50 if you try. and use them, especially if the line is big.
disney is much better. do get the hopper pass (i think thats what they call it) you can go between all 4 parks, and they have free shuttles running between all of the parks too. and if you can stay at a disney hotel, they have a bunch of them. you get cool free stuff, and you get into a park an hour early every day (different park every day) all i can really say is do everything. mgm studios was my favorite, lots of fun rides, jsut a fun place. whatever you do DO NOT miss the fire works at epcot every night. thats the only one we caught and i can say its undoubtedly the coolest thing i've ever seen. iits worth going just to see the fireworks.
theres a good hooters down there to.