I have no experience living in the ATL area but I have lots of experience shopping for a house there and have searched both north and south. Please take my comments knowing that I have .01% of the experience compared to many who post here but I thought I'd share since I'm in a similar position to those thinking about moving here.

I would prefer to live on the north side and have better access to Costco, the forests/mountains up north, and the lakes. When I went house hunting up north I found the homes were pretty much the same as the south side, just closer together and more expensive. As this will be our 12th move in the past 20 years we've figured out what we like and don't like in a house which means we're probably going to build. I found several custom builders in/close to my price range on the south side, the only builders I could find on the north side which I could actually afford were puppy-mill wal-mart builders like Lennar that build junk houses and can't/won't customize. Even so I found a really nice home in Kennesaw which I thought about putting an offer on. The small garage and no yard were big negatives, but the final nail in the coffin was the traffic. Sun Tzu said your yourself and know your enemy. My enemy is traffic and I lose about 2 years off the end of my life for every hour spent going nowhere for no good reason. I'd go insane making that drive once a week. No matter how many times I told myself how much cooler and hip the north side was, the reality of the traffic and home bang for the buck drove me south.