I've stayed at mgm many times. I've been in celebrity spa suites twice (these are larger than standard rooms--but IMHO not real "suites"--it is one big room, with a separator between the lv and br.)
The regular rooms, are all pretty much identical--some have nicer views than others. I'ver never stayed in the west wing, but passed through (there is a "secret passageway" from the mansion gaming area to las vegas blvd exit, bypassing the slots and racebook area) and looked into the rooms while they were being cleaned--not too impressive.
MGM has lots of rooms and waiting for elevators at times can be annoying--long lines form. There is a section (rooms identical to those in the main bldg) with only two or three floors--you never have crowds or wait for an elevator--but since it is close to ground level street noise can be annoying.