Shooting both back to back on the same day with the same ammo, the long slide cut groups by about 1/3. Longer sight radius helps clean up sight alignment errors, and the match fit barrel improves mechanical accuracy. Adjustable sights are also a huge benefit so the pistol can be zeroed. Will have to bench them both to determine how much actual mechanical accuracy difference there is.
The long slide also shoots a bit softer, but the VP9 is already a soft shooter so it’s kind of a subtle difference.
Hit the range twice last week with my brother and my dad, brother is carrying a Gen 5 G19 MOS with a Trijicon RMR. I got some time on it as well, the RDS is pretty slick on a semiautomatic, I’ve also shot an M&P with a Leupold Delta Point and liked the RDS. Even with the superior sighting system the Glock could not match the accuracy with the ammo we had of the stock VP9 in my hands. My brother was disgusted that I handily outshot him with his own pistol (hey I used to be a competitive bullseye shooter...) and even more disgusted when he outshot his pistol with the long slide VP9. Very pleased right now with how good the barrel and slide are fit on that kit.
Now to get it milled for a red dot sight.... the dot is worth the time to learn. Yes I can shoot nice groups with iron sights, but it takes a lot of concentration and that is fatiguing. It was pretty damn easy to shoot that G19 with a dot on it consistently, enough that I’m confident I was getting representative accuracy out of it. With a dot all I had to do was manage the trigger. So once the Aimpoint ACRO P-1 comes out I’m sending the long slide off to get milled, and probably send the frame in to Lazy Wolf Guns for some texturing and a trigger job with an emphasis on cleaning up over travel and reducing the reset.
Unfortunately the Glock 19 still doesn’t get along with my hands, the trigger guard needs a deep undercut to not chew up my middle finger, the stupid cutout in the front of the frame irritates my pinky, and the top of the frame beats up the knuckle on my shooting hand thumb. Maybe I should try a G17, the grip on the G19 is just too cramped. At least they got rid of the stupid ass finger groves that fit no one.