35mm vs 50mm for baby pictures

thank you very much for any help.  thanks to your advice, I bought the D5100 camera with the 18-105 lens.  this is all purchased for my wife as we have a baby set to arrive in 6 weeks.  based on what I've heard, I need to get a macro lens with better f stops than the 18-105 I bought.

so, to take pictures of the the baby arriving in a couple weeks, should I get the 35mm or the 50mm lens for her?

I have one prof photographer friend saying 50 and another saying 35, but both are shooting full frame cameras, so I thought I'd come back to beg you gentlemen and ladies for help another time.

i know I need to get one of these lenses, but just can't decide on which.