I also much prefer Universal Studios. I preferred IoA during my roller coaster fanatic phase, but now I don't really even like IoA much except for the water attractions. Since there are Potter fans in the group, I would also say Diagon Alley is an absolute must-see. Hogsmeade is very underwhelming by comparison, although I do like Forbidden Journey more than Gringotts (I've only ridden Gringotts once, though, and I hear it gets better after riding it a few times). I agree that Studios is more adult friendly for the most part. Seussland makes up a huge portion of IoA, and it is a downright snooze if you're above a certain age.