I have only been to Sea World San Diego. I really enjoy going to the park though I miss a lot of the things that used to be there. Like the Clydesdale Hamlet, the pearl diving pool, the old Captain Kids play area,etc. My favorite animal exhibit is Rocky Point (dolphins). I love the green space and the flowers that seem to thrive in the park. Hopefully that is something that stays in the parks. I don't go to Sea World for the rides, I go for the animals. The only rides I ride there are the Observation Tower and the Sky Bucket-type ride. There used to be a boat ride along Mission Bay but it disappeared a long time back.
The food at the park is some of the best I have ever had at a theme park. The sandwiches at the former Busch Hospitality House are really good and the pasta place (sorry can't remember the name) had some very tasty and filling pasta dishes.
Having been to only two of the parks, Orlando and San Diego, it is hard to judge. I'm going to cop out and say that I think they both have unique aspects which make them special and I enjoyed them both for different reasons. Most recently, Antarctica became an additional reason for me to love Orlando. I DEFINITELY want to go to SeaWorld San Antonio though to compare.
We've been lucky enough to have visited all four SeaWorld parks (including the dearly departed Sea World Ohio). Each has/had its own unique personality while also containing many of the familiar SeaWorld traits. San Diego is somewhat compact with a very nice setting on the bay. San Antonio, on the other hand, is spread out and easily the most spacious of the parks. Orlando is probably the most "complete" SeaWorld in terms of attractions, exhibits, and shows. Ohio was a very pleasant park with a nice semi-wooded setting beside Geauga Lake. It was sad to see the park fade after being sold to Six Flags.
I'm actually going to go out on a limb and say I enjoyed Orlando slightly more than San Diego...but then again it's been a few years since I've been back to San Diego and I haven't seen the new entrance yet either! Planning on doing a super fan meetup there this next year and I'm looking forward to it!