drop them both and find a better RB situation to dip into. Take a flyer on Starks returning, or Mike James, or Dixon, or Bibbs in Denver. You didn't mention how deep the league is, but if I can avoid the NYG backfield I will.
If I had to choose one, give me Perkins just on upside. At this point we all know what Jennings is. Perkins still has some unknown to him, and maybe he'll shine if given the full workload, which I don't see them doing unless Jennings goes down again. Last time Jennings went down, Perkins had Vereen in his way.
If you're asking which one to start this week? I guess it'd have to be Jennings, but :X