I think I commented on this somewhere else at PF, but... The mag well of the gen5 G19 creates a swell at the base of the grip that intersects with the base of my hand, giving the gen5 a "bigger" feel than the gen4. Then, add the height of the of the hump on the backstrap vs its height on a full size (17/34/45) receiver.
For those reasons, if I was going to be a dedicated 19 carrier again I believe I would cut a 19X or a G45 vs the gen5 G19.