Aquatica and Busch Gardens Africa are as different as night and day, so it's hard to say which one you should choose.
Aquatica seems to be a very nicely landscaped and colorful water park with a few animals thrown in the mix. The attractions it offers are not much diffrent than many other water parks across the country. However, if you only have one day, don't want to travel far from your hotel, and want to relax and play in the water, then Aquatica may be a good choice.
Busch Gardens Africa is a huge world class theme park with a multitude of thrilling rides, family rides, first class shows, tremendous up-close animal encounters, and a beautiful spacious atmosphere. It's a park where you could easily spend two or more days fully exploring all it has to offer. It is about an hour+ from Sea World, but it would offer a great variety of opportunities to entertain your family and allow them to explore amazing surroundings. If you have the time, Busch Gardens Africa is well worth visiting. It's one of my favorite places to be.
I believe the multi-park tickets on the "visitors" page of the SW/BGA/Aquatica websites allow for seven days of admission to the chosen parks. If you will be there for a week, you could easily spend two or more days at each park. You could even buy a three park ticket and spend one day at Aquatica, two or three days at SW, and two or three days at BGA.