I was very disappointed by the Hogsmeade area at Universal. It's tiny and has very little in it -- and I think they made a huge mistake putting the ride inside Hogwarts. I know people absolutely love the ride (I hated it because it gave me the worst motion sickness I've ever had, even after taking a Dramamine -- I thought I was going to throw up for a good 30-45 minutes afterwards, and it also hurt my GF's neck), but they could have put it somewhere else or designed the area differently. It was a seriously missed opportunity to not have a bigger Hogwarts you could explore, visiting the different classrooms, having a restaurant in the Great Hall, etc.
Diagon Alley, on the other hand, is tremendous. The way it's completely hidden from anywhere else in the park and that you have to go through a little alley and then it opens up in front of you is just wonderful.