I predict it'll be the Falcons. Atlanta has the #1 offense in the league this season. While it's been proven in the past that the top defense will usually triumph over the top offense, New England's defense isn't THAT good.
...Right now I'd put my money on the Falcons. Based upon their difficult schedule, communication during plays and overall fundamentals. They seem to run strong, solid plays every time making them less reliant upon long third down conversions.
..I think that it will come down to whether or not the Falcons defense can put pressure on Brady in the pocket.