I love GA, and we have season passes, but I'm totally an upside down super fast coaster kind of girl.
The main park only has a couple of water rides. I've never been to the water park but it doesn't look like anything exciting IMO. I've never been to Dorney either, but Brian loves water parks and prefers that one over the GA water park. I don't know abot the pricing at Dorney, but at GA it's a separate fee for the main park and the water park so that may be something to keep in mind. The food at Ga is typical amusement park food... just ok and definitely overpriced. The atmosphere... it's become slightly more annoying to me lately. But maybe I'm just getting old . So many teenagers running around, line cutters, obnoxiuos people walking backwards and bumping into you, etc.
So if you are mainly looking for water stuff, I think Dorney might have an edge over GA.