I've not fired that model Sig. But I've yet to see one that didn't live up to the motto of To Hell & Back Reliability. The FNP is a great weapon also. I'm not being on Poly frame pistols but both those have the one thing I want to see on any weapon..A hammer.
I own a couple Sig Sauer pistols and have the Browning Pro 40 which is the same pistol as the FNP-40 and I simply love it. hear those poly Sigs are good weapons too. I'd say you can't go wrong either way. Both have a De-Cock But the FNP has a manual safety. Rather that is a plus or minus is up to you.