I've got a SIGPRO SP2022 in 9mm that I ALMOST didn't get in favor of the FNP. Like you said, the FNP was about $100 less, and came with 4 mags - whereas the sig only comes with 2. 2 more SIG mags is another $70, so factor that into the decision if you want more than 2 mags.
I like the SIGPRO although I don't just love it. The trigger can be a little creepy sometimes, and the grip is pretty big. It's accurate enough, though not stellar, and you may find that the finish on the barrel wears off VERY quickly - so quickly, in fact, that I took a brillo pad to the outside of the chamber block because I just couldn't stand the AWFUL scratches it was taking on from the slide.
I've got an HK P2000 that is miles ahead from a quality perspective - fit, finish, accuracy, everything - much much better.
I do like the SIGPRO SP2022, and it fits a great role in my collection - it's my car gun. But if I was investing in something special that I wanted to shoot alot, I don't think I'd get it again.
I'd take a good, long hard look at the FNP. FN makes excellent weapons and is generally considered to be an underrated bargain in the handgun world.
If I had to go back, I might just have an FNP right now. Just my $.02
NOTE - I've heard many times that the classic P line of SIGs is better quality than the SIGPROs. Just FWIW - not trying to bash anybody's guns here, just my experiences