I have had a FNP 9 for a long time, Excellent gun.
I can not agree on the FNX I bought the FNX 45 thinking it would be as nice as the FNP 9. No way. It is barely combat accurate, the rear grips are held on by a small piece of cheap plastic and moves up and down a good 1/16" I called FN and they say it is normal and "within specs" I thought it was cheap construction. I wedged it with a small piece of cardboard. The little tab looks like it will break off in no time. I went to the LGS and checked others and they all did it.
The FNX 45 functioned fine, but shot way low and there is no changing of sights. FN CS was hard to deal with, heck mine came with a photo copy of the manual, I wrote them and asked for a real version. Stated out of stock, waited several months still no manual. I disliked the gun so I traded it for something that was accurate.
The controls of the FNX are like a poor mans HK.
I do like the FNP version at least the grips are held in with a screw.
JMO. maybe the 9mm is better.