Read CK1's post first, very well said.
I have a MPX PCC. I got it about 3 months ago right before the current mess we are experiencing. I was tired of messing with the Glock mags and extensions, Failure to feed etc.
I'll add that my MPX does not care what I put in it and it runs. 115gr, 124gr, 130gr Syntech 147gr, Federal 150gr Syntech and my HST hollow points. They all run with no issues. Added TTI mag extension and worked right out of the box with no issues, filing grinding or sanding needed.
All I can add to the JP side is they are very nice guns and the ones I have seen run very well. As CK1 said, once you start messing with any them then things start to get sketchy.