Should I start LeSean McCoy or Quintin Ganther this week in my flex spot?

It's week 14, and I NEED a win to get my playoff spot in this years fantasy league. I have a solid starting lineup, but I have one question. As far as my flex spot goes, I have usually started LeSean McCoy. However, I recently picked up the new starting running back for the Redskins, Quintin Ganther. LeSean plays the Giants AT the Meadowlands, and Quintin plays the Raiders AT the Black Hole. I am just interested in a variety of your opinions, and obviously some stats or facts to back it up. Any help is appreciated.