Foles is on a team that runs very little. This may be the one season the Eagles under Reid reach just below the NFL average in running plays. Pittsburg wants to run and faces the sieve that now is the Ravens run defense. Foles should significantly outproduce Leftwich assuming your league doesn't unduly punish turnovers. I'm unsure what your 1 or 2 week rental comment references, but it would surprise me if Vick starts another game for the Eagles. He's about to be a free agent and Foles is supposed to be the future.