Definitely Wet'n'Wild. They have better rides, and they have two new rides - the Surfrider and the Kamikaze.
It would be winter in July. The parks would still be open, since we don't have snow or anything. I went to Wet'n'Wild in almost-winter, and we were freezing our arses of, but we still had heaps of fun! xD
My daughter reckons Wet n Wild has more rides, however you can get a pass to both White Water World and Dreamworld which might be a better deal. July can be quite cool so spending 1/2 a day at both would be my choice. Check out worldsinone.com.au GET DRENCHED, GET DRY! Have fun.
wet n wild is wayyyy better. i have yearly passes to both wet n wild and white water world, i went on every ride at white water world before 2:00 pm the day i got my pass. plus wet n wild was voted the best waterpark in the southern hemisphere
They're quite similar, but white water world is newer.
Are you planning on going to any of the other theme parks?
You can get a discounted ticket if you want to go to more than 1 theme park but they have to be the affiliated parks.
You can get a day pass for white water world and Dreamworld or a 3 park super pass for wet'n wild, seaworld and movieworld.