We just went to Aquatica for the first time last week. Had a great time. the park is beautiful and clean. The consensus among the family (grandparents, husband and kids) was that wet n wild had more. Wet n wild is more cement and not themed but had lots and lots of different slides. Aquatica is more tame.
My kids were younger when they went to wet n wild (probably about 5 and 6) and they loved their kids area. Aquatica had a similar area, but they were too old now (7 and 9) to go there! Can't give a report on it.
For the money, Wet n Wild is quite worth it. If you want tame rides and a day in the sun and have passes to SeaWorld anyway, Aquatica will fit the bill.