As far as my own opinion on SPG hotels in the Atlanta area:
Westin Airport & Sheraton Airport are about equal, both nice with the Westin just at a slightly higher level. Both have club rooms.
Sheraton Downtown- about 3 blocks away from the main downtown area, next to the highway. Its a large remodeled hotel with comfortable rooms, and a nice club--but can be confusing given there are two wings quite far apart. The area is not the 'best' in the evening--fairly deserted.
Westin Downtown- seen better days, its the round building with a revolving restaurant on top.
Sheraton Buckhead- formerly a Four Points, right across from Lenox Mall, but a bit far from the Buckhead nightlife scene. It too was recently remodeled and is pretty nice. It is close to the MARTA stop at Lenox.
W Perimeter- at the northern edge of the city, across from a large shopping mall. Very typical of 'W's everywhere, sleek & modern.
Sheraton Colony Square- I know lots of people hate this property and yes, I agree it has seen better days. But as a Platinum SPG, they always have treated me very well. It is in the midtown area, with lots of fun restaurants and Piedmont Park is close by.
Hope this helps.