The Sheraton in Cha-Am is really nothing to write home about, unless you can dwell in a pool for hours on end. There's nothing wrong with it, but the rooms are really... Sheraton. It can be had for rather reasonable rates, though.
The Sheraton in Pattaya is a completely different style resort, though. The pools aren't that great, but the villas can be nice if you manage to get upgraded to one.
Neither property has a very good beach.