Colony Square is located in Midtown, which is closer to the downtown area and has some fun/ funky restaurants--but otherwise some of the rooms at the hotel are in desparate need of updates.
Sheraton Buckhead, as stated is right across from Lenox Square Mall and in the suburban area of Buckhead. There are a couple of other options if you want to be downtown--Sheraton Atlanta close to the 'heart of downtown', the Westin that has one of those big revolving dining rooms on top. Or if you have a car, there is the W at the Perimiter which is north of the city (again next to a shopping mall).