I've been to both, and I have to say I like SeaWorld Orlando better. There isn't a water park in Orlando, as there is in San Antonio, but that hasn't been an issue for our family. There is Shamu's Happy Harbor in Orlando which is a water play area for kids, but that wasn't an attraction for our kids either... they just want to see the animals. San Antonio has more rides than Orlando, but the animal displays are much better in Orlando. Wild Arctic in Orlando is neat with the motion simulator at the beginning (you can bypass this if you want), and the belugas and polar bears inside the attraction. The Dolphin feeding area in Orlando is much nicer, and larger than San Antonio.
Both are good parks, but very different. I wouldn't rule out going to Orlando just because you've been to San Antonio.