There has been a lot of info on the boards recently, so if you can manage a search, it may help. Since no-one else has answered, I will jump in....
I am considering the Atlantis, so here is what I can tell you. Booking a room at Atlantis can be pricy. Starting at well over 200.00. Atlantis, and the Comfort Suites across the street, offer Day Rooms, if available, first come first served, in person only... (won't even acknowledge that this is done over the phone or internet in advance.) I understand that they start at $200.00, plus taxes and fees.
Rooms at the Comfort suites can be reserved, at the Comfort Suites web site, at an internet users rate of about $175.00.
Getting a room is the ONLY way to have access to the pools, slides, beaches. And, of course, also includes The Dig.
Hope this helps!