I bought a PPQ and a VP9 at one time.. Sold the PPQ as I could never be satisfied with the grip. If I put the small insert I see my self pointing left after a draw, If I put the large insert I cant wrap my hand around comfortably. If I put the medium insert it leaves a gap between the web of my hand and the top of the frame just under the slide (The beaver tail area).. As such the gun pivots about the humb in the back of the grip and I cant get a controllable grip on the gun.. The trigger on the PPQ is top notch, but I come from a glock platform and I am used to a high grip where i push the web of my habd all the way up in the rear of the frame top.. I couldn't get such a grip on the PPQ no matter how i tried.. I wished that PPQ could put some extra material in their medium grip insert at the top to fill that gap in my hand.
The VP9 on the other hand had the best grip and I can control the gun with a much positive grip allowing to ride the grip high as much as I can.. The trigger is also excellent and very easy to control..
That said, If I get to choose between a PPQ and a VP9, I will go with the better grip because it gives me more control-ability of the gun and that would be the VP9.. Don't waste your time comparing the triggers of the PPQ and the VP9 there are two groups on each side of the fan fence.. In short both are great, The reset on the VP9 tipped the balance for me and the grips and control ability.. Also the rear sight on the PPQ felt so complicated and it felt like it might break or something.. The VP9 rear sight is much more robust.. Hope this helps with your decision.