I have a feeling 99.999% of the folks here will say to go for the M&P, and I can't blame them since this is an M&P message board. Same thing would happen if you go to an XD board, they'll most likely say get the XD. I personally do NOT own an M&P, but I hear almost nothing but good things about the pistol, and the few complaints are typically small stuff. To me, it seems like one heck of a great gun.
I DO, however, own an FNP-9, and plan to get another. Maybe even a .40S&W one (or two) as well. 9mm's that I have fired before the FNP-9 were the Beretta, and H&K. Did not like the way they shot. Didn't either of them. I was skeptical of getting the FNP9, but did so because my LGS guy swore by 'em. I got the stainless bi-tone one with decocker. Comes with 3 mags, either 10 round or 16 round (depending on your state laws). Very well put together. Replaceable steel rails. Very good sights even though the one I have isn't night sights (I really don't care). Has interchangeable backstraps similar to the M&P. It is not striker fired, it's traditional DA/SA exposed hammer.
When I took it to the range for the first time, the grip was comfortable for me. My first shot was dead on. It shoots where I point very easily. Even my buddy liked it very much, and wants to shoot it again. Since then, I've put about 200 rounds through it. Not much, I know. But I have 0 FTF's, and 0 FTE's. Spits out anything just fine, and begs for more. I personally like the trigger pull. And she's VERY mild on the recoil/muzzle flip department. It's fun to shoot. Easy to shoot all day long if you wanted to. Clean-up is easy. Take it apart like a Sig. Good controls, that don't get in the way, but are in easy reach. I love this gun!!!!!!!!!!!!!!!!!
Comparison:
FNP-9
External Hammer
3 mags
Loaded chamber indicator
Decocker (ambi)
Mag release (ambi)
4" Barrel
Stainless steel
Poly frame
M&P
Striker
2 Mags
LCI type
Mag release (ambi)
4.25" barrel
Stainless steel
Poly frame
Try them both. Both are winners in my book. Get both if you can.