I have a FNP-45 with several 15 round magazines. I LOVE IT!!! My only complaint was that it was difficult to find a holster. The one I have and love is Desantis basketweave with a thumb break.
http://www.opticsplanet.com/desanti...ed-thumb-break-scabbard-3-slot-001bg31z0.html
The FNP-45 has been replaced by the FNX-45. I haven't seen any real difference between them other than the name but supposedly they made some improvements. The FNP-45 is a DA/SA trigger so as long as you are ok with that it should be fine.
The Sig P220 is a great gun and I have several. I simply carry the FNP-45 more for the larger capacity. Both shoot great.
I also love the H&K USP. Both the H&K and the Sig will cost you more than the FNP-45 or a XDM/Glock/S&W.