It does not compare.
Atlantis is amazing.
We have been to Atlantis, Coney Island, Conneticut , Coral World in St Thomas to name the highest profile ones plus a bunch more.
Atlantis to me was by far the best.
Although if you have the time Living Seas at Epcot is a nice attraction. They rehabbed one part of it themed to Nemo.
If you only have one Epcot day and are really pressed for time you can skip it but if you have a park hopper and are doing multiple days or are not planning on much at the World showcase give it a shot.
I would not go to Sea World. We went on our last trip (#11) for the first time and it was a huge dissapointment and a waste of $$$.