The higher the MPF is always better with regards to playability. That number is the result of an overall calculation based on the parameters you mentioned, and others. Generally, the higher the playability, the longer the C-deimension, the lower the actual vcg, the more rearward the cg and the higher the MOI. However, you can have, and often do, a club that might have a higher vcg that is rated higher than one that has a lower cg due the c-dim or the rearward, or a combination of both. Although the actual vertical is very slightly lower in the P790, its c-dim, rearward cg and MOI are lower than the JPX 919 Forged. Calculating all the factors puts these two irons 79 pts. apart, which is not that much. Ralph has often stated that for most players it would take a 100 point variation to notice a difference. Still, in my opinion, and if the cosmetic, feel, sound, etc. are all comparable with no preference, why wouldn’t you want to go with the design that has a higher playability? Stability comes fro the c-dim and rearward cg’s. Feel and solidness of contact comes from how easy it is to driver the vertical cg of the club below the balls cg and how close to the cg the strike is, both in the vertical plane and the horizontal. One thing to note, the horizontal cg on the P790 was .094″ toward the heel of the club. The JPX 919 Forged is .021 towards the toe. That is 2.92mm difference (.115″). That might not seem like much, but that contributes to the c-dimension number and ideally you want to see the horizontal cg in the center of the face, but if it’s not, slight toe side is better than heel side for stability.
The JPX 919 Forged c-dim, vertical, rearward and MOI are on our website. Final rating was 619 points (Game Improvement category). C-dim is 1.354, actual vertical is .793, rearward is .514 and the MOI is 14.1744.