I haven't heard too much on the FNP40s, but I can vouch for the XD line of guns since I've owned 2 of them in the past. Never a FTF or anything. The XDm has 16+1 rds of .40s&w (or was it 15+1?), and best of all it has a match barrel.
Bottom line, you simply can't go wrong with the XDm as long as it feels good in your hands that is. Also, the trigger is consistent and IMHO pretty darn nice for a stock gun. You don't have to get used to transitioning from DA to SA like you do with other guns like the FNP40.
I'm not knocking the FNP40 at all. I own a H&K USP compact (v1, DA/SA w/ safety and decocker) and it is my favorite polymer handgun that I own. But the transition from DA to SA is still something I don't exactly look forward to when shooting it. It's more of something I accept because I like the gun so much and I'm too scared to try the LEM trigger!
Anyways, I would personally take the XD over the FNP, but that's just me. Good luck!