After a long evaluation and a borrow of one, I bought a PX-4 9mm yesterday to "celebrate" the president elect.
Just for reference I have owned or heavily used the following poly pistols:
M&P9 (still own, my wife's favorite)
XD-9 (gone)
Walther P99 (gone)
HK USP 45c (gone)
Glock 17 (rented)
Glock 20 (borrowed)
First of all, the PX-4 is pretty darn accurate and soft shooting in my hands. It doesn't seem to suffer from balance problems as it empties.
The one I borrowed was stone reliable, I expect no less from mine. I have owned about 8-10 other Beretta duty sized guns and none has ever failed.
The PX-4 has a good spread of size options to get its grip right for the hand, though changing them is pretty hard compared to the S&W or Walther. I got rid of my XD because I couldn't alter the trigger reach. The PX-4 is better vertically in the grip length than the M&P which rubs my middle finger with its trigger guard.
I like the aggressive checkering of the polymer on the Beretta. Not too rough and not too slick. The XD sucked in how smooth it is. The Glocks have idiotic built in finger bumps. The M&P is pretty nice too except for the rubbing.
I like having a hammer. Though I own and have fired striker fired pistols, I trust a visible hammer more for some reason.
I'd rather have a trigger disconnect than a mag disconnect.
The action is smooth. I like that it uses a locking block rather than lock squared on the ejection port. A block is a cheaper part to replace than a slide.
The glow in the dark paint on the sights is surprisingly good on the PX-4. When I first encountered it, I wasn't expecting much, but they didn't cheap out on the paint mix. There is some serious europium oxide in that paint.
I really like the pistol. The trigger being DA/SA probably keeps it from be objectively the "best." It's more like squarely in the "great" territory with the S&W and the Glock, but better than even the H&K of my experience.
My only other minor complaint is how tight the last four rounds into the mags are, but Beretta was wise enough to include a mag loading tool and they will eventually loosen up to the edge of thumb busting, like most Beretta OEM mags.