It was really interesting. I loved seeing how they made everything work and the visual tricks and props that were used. And just seeing how much effort had to be put into everything. The kids had fun as well. But if you have to choose one I'd go to Universal Florida (not California) as that experience is more like being in the actual Harry Potter world.
haha, I still have my Harry Potter passport too! I bought a collectors set of the books in England...they were so heavy to lug around during the trip, but completely worth it.