I have both....my story... injured my wrist so could no longer shoot pistols. Thought my shooting days were over and then PCC was born. I bought a MPX GEN2. Ran for the first 1000 rounds and then I couldn't get it to run, even after 2 trips to Sig. Gave up bought the JP. It is heavier than the MPX but boy it RUNS. Nothing better than to not have to worry if you gun is going to function. However my wrist was getting worse, I guess because of the weight of the JP and the NEW barrel and hand guard was not out yet for JP and SIG came out with the Competition new and improved MPX sooo you guessed it....The MPX runs and runs BUT you have to clean piston and tabbet every 1K or so. STILL worry about it not running. Ordering the new barrel and hand guard and short stroke system for my JP, why you might ask, I just LOVE that JP. Confused? Me Too.