Interestingly enough, I have been looking at these very same 2 pistols. And, after holding them both, I have pretty much settled on the Ruger. It's slimmer, much, much slimmer, and holds 17 rounds in the mag. Plus the bore axis on the SR9 is lower and the gun just feels much better in my hand.
I'd still like to have a FNP9 or FNP40 though. And I really wish Ruger would hurry the heck up and come out with the compact SR9 already!