Personally, I would go for Disney.
LA County Fair: Let's face it. We all are going for just the food. There's some nice exhibits, but its all about the food. Disney might help with that remedy.
Sea World/Belmount: I'm disgusted you'd bring this up. They torture their wild life! Joking aside, unless you need the credits, this wouldn't be my first choice. Manta is a REALLY good coaster so there's that. Belmont is a nice little boardwalk park with a nice beach, but the Giant Dipper isn't a very comfortable ride IMO.
Universal: I'd wait a couple if years until Potter opens.
Disney: Good food great rides. Go for this.
Hope this was helpful.
I'm trying to make a longer trip out of this. I want to go to Disney, Universal and SeaWorld additionally... I haven't been to the west coast since I was a baby so I want to do all I can!!