Jesper,
I went to both shops the beginning of last December. The AAA Hobby is certainly just a model shop with a decent selection, and a nice array of aftermarket, tool, and other supplies, but it isn't large. They will special order, but I didn't try that.
The HobbyTown USA store in Kennesaw, GA is the largest HT USA I've seen, and it has a row of shelves just for Military Vehicles, another for Air Craft, another for cars, another for figures, and so on, along with AM PE sets, tools, building supplies, books, etc. It's still an all-in-one hobby shop, but the store is huge (im' guessing it was originally one of the multiplex theaters that they later knocked most of the interior walls down).
840 Ernest W. Barrett Pkwy NW
Suite 650
Kennesaw, GA 30144
(770) 426-8800
http://www.hobbytown.com/Store/Profile/GAKEN/If you pm me your e-mail, I'll send you one of my AMPS chapter's newsletters that has a store trip report in it with photos for both stores. i would stop at both if you will be there for a couple months.
Good luck!