In my opinion, this is a tough call. If Rice is going to have a breakout game, it could be against Miami (who got shredded by Sproles).
Powell is the only real weapon for the Jets (aside from Kerley) this week. He'll see a lot of touches, but will also be keyed in on bye the ATL defense. Also, ATL could put up a lot of points on the Jets early and force them to abandon the run.
I think Ray Rice (if practicing and healthy) is the better option this week, but it's really close.
Good luck! Hopefully someone else can share some more insight on this.