I have been to all three Sea Worlds in US: San Diego, San Antonio and Orlando. And I think Sea World San Diego is the best one. Shamu in San Diego is super huge! Encountering beluga whales and turtles are unforgettable experiences.
If you are traveling to San Diego, purchase San Diego City Pass ticket which include Sea World and famous San Diego Zoo Safari tour. Some passes also include Lego Land in Carlsbad, a 45 minutes' drive from San Diego.