Frankly, I think there's no favorite this year in 7A. That makes it much more exciting. Every 7A squad has some kind of noticeable drawback that could make for an interesting season.
In terms of elite 7A teams, I'd go with Buford, Mill Creek, Grayson, and North Cobb. Colquitt can work their way up to that status with a strong opening few weeks of the season. North Cobb is the most likely to lose that distinction of elite early in the season.