Looks and price as far as I can tell.
I got the JM mainly because of the full under lug, (Matches my 617 and 686.) The trigger might be a bit smoother on the PC version, but I can hit 6" steel at 75 feet DA, 2 handed and standing. After about 500 rounds will probably change out the springs for the ones Jerry sells. The grips on either I would change out and really do not like the ones on the PC version.