I'll gladly share my perspective on a couple of your choices, you have a tough decision to make. Went to the range yesterday with the VP9, CZ SP-01 Tactical and G19 with RMR. Shot about 150 rounds through each, quick fire from draw into paper plates mounted on cardboard at about 10 yds. With all three, was able to keep the shots all on the respective plates, one for each weapon. The VP-9 had the tightest group of the three, centered on target, the G19 was nearly as tight, about an inch and a half low (will check the POA/POI of the red dot another day), and the SP-01 was a bit looser pattern than either.
Of the three, the VP9 feels best in my hand, with the adjustable hand swells and back strap, you can really fine tune the grip to your hand. The SP-01, with the factory rubber grips, was also very comfortable, not quite as fine tuned to my hand as the VP9. The Glock, well it's a Glock, what can I say.
Recoil control went to the SP-01 due to it's weight, I perceived the recoil control of the VP9 was better than that on the Glock, but I attribute this to the red dot bouncing so vividly in front of my eyes. Getting back on target was about the same, however, with the Glock and VP9.
Not telling you anything you don't already know so far and what I have yet to say is nothing new either. I am not a target shooter nor am I a competition shooter, my weapons are merely for carry/self defense. The accuracy and proficiency I had yesterday with all three weapons is well within the realm I expect from my defensive weapons. What really sets the Glock above the others, for me and only me, is the sheer simplicity of the design and my ability to completely take down the weapon using a small punch or Glock tool. This point was really driven in to me when I compared the armorer classes by Glock and SIG Classic series. At the Glock class, you are given one tool, a small punch. At the SIG Classic armorer class, you are given a small assortment of tools. Don't get me wrong, the SIG Classic pistol is a simple design, much more so than either the VP9 or SP-01. When I start looking at the FCU on the P320, that simplicity is out the window.
In terms of a defensive weapon, the G19 is still my go to, one is mounted on my bedside, one is locked in my car for everyday use in an Andrews Custom Leather Carjacker and a third rotates in and out of my EDC rotation. Between the four choices you listed, the G19 would be #1, the M&P #2, the P320 #3 and VP9 #4 based merely on my needs and expectations in a defensive weapon - ease to bring back into service quickly and easily regardless the severity of the failure and has adequate accuracy in my hands.
If you are only to get one, the G19 gets my vote. I really like what S&W has done lately with their triggers. They are on par with Glock in terms of simplicity, but replacement/spare parts proliferation falls woefully short of what is out there with Glock. Regardless, I don't think any of the four choices you are considering are a wrong answer. I wouldn't mind depending on any of them to defend the lives of my loved ones or myself. Good luck and happy shopping!
