you have two great carry guns, the XD and the FNP, both have holsters available, and both are very robust and functional guns.
Context is everything. Where do you live, what are the "odds" you are going to need something? While some may scoff at this, it has great bearing in my mind on what to carry. If you live in a rural area where shooting a stray critter is not unheard off, I would suggest the 686, which while not a lightweight, is not a total beast to carry either, a few million cops carried them for decades without any issues. If you manage a KFC in DT detroit or a stop and rob in Atlanta, i would say carry both the XD and the FNP. ( only slightly kidding)
First thing to do is get a good belt, made for carrying a gun from, A very good one is either the double thick (two layer) belts from LL bean, and Cabela's, which is available for under 40 bucks. IF you do not have a good belt, the holsters do not ride like they are designed to, and you end up with a less than satisfactory result. I tried for a few years to get by with just a good work belt, but they would just break down shortly, and the gun and holster would start to sag and wobble.
Start with one good OWB leather holster. I like the askins styles, like this. Fairly high riding, it hides very easily under a camp shirt or un tucked Polo.