I have shot the PX4 in 9mm and 40 cal. In 9mm - it seems like a standard DA/SA w/ external hammer. Nothing stands out. In 40 cal - wow. The rotating barrel doesn't do much for the 9mm round, but in 40 cal, it seems almost like shooting a 9mm. I am impressed at the recoil reduction.
I'm not really a fan of the 40 cal - however.
The trigger on the PX4 is just so so. Kinda like the 92 trigger to me.
As for the FNP - The DA pull is the smoothest I've ever felt. I've only dry fired a couple - but I was impressed.
I think that if ya want a 9mm, I'd get the FNP. In 40 cal, I'd get the PX4.
Come check out www.fnforum.net if U wanna know more about the FNP.