There are some delusional people in this thread, Federer's backhand is definitely better right now especially on a hard or grass court. Nadal's backhand used to be a damn good shot but it's deteriorated into a weak push. He really can't do anything with that shot any more and is utterly desperate to run around it to hit forehands (even more so than Federer).
On the other hand, IMO Nadal's forehand is currently better than Federer's on most of the tour surfaces. Federer's forehand is still easily the second best on tour and by far the best on faster surfaces and indoors but overall Nadal has it these days by a decent margin.