You really just have to read up on both and see what suits you best. The respective sites have the information you need to asses this and it's clear that you need to spend some more time on both sites. I'm pulling my NFCU info from their site since I'm not eligible and don't have any NFCU products.
If you're already accruing MileagePlus miles the 1:1 transfer from UR to MileagePlus is probably beneficial. NFCU points are worth 1 cent each when redeemed for airlines tickets and less when redeemed for cash. UR points redeemed as cash back are worth 1 cent each but the better value is typically via transfer to travel partners. The rewards earn rates differ on the two cards but that's also covered on the respective sites.
Last edited by takeshi74; Oct 10, 2014 at 11:42 am