I'm thinking about including a Disney and/or Universal trip as part of our California trip this summer (most likely mid- to late July). We've never been to Universal (FL or CA). We've been to DisneyWORLD a few times, most recently 3 years ago, but never DisneyLAND.

My questions:

How much time do you need for each park?

If you could only do one, which would you do?

How good is the Harry Potter stuff at Universal Hollywood vs Universal Orlando?

Are there any special passes or early admission things that are worthwhile? I feel like I'm trying to explore a whole new world and don't know the language.