Rom, it's a couple little things. Mag capacity, the lack of a loading port that one can use for a fast reload or ammo switch, and on older ones the lack of an interrupter, the slam fire feature that some regard as a plus.
Also, for armory storage and the range, the lack of an easy indicator to show the weapon's empty is naother small but important point.
Don't get me wrong, the 37 is a fine design and a case could be made for it's being the BEST upland pump ever made.
RE the stock, I can reach the tigger fine, but there's not enough curve to the PG for my two smaller fingers to get the grip I'd like them to.
This only applies to me, of course.