Originally Posted by papercidal
For the most they are identical in size, trigger reach may be a little less on the gen 4 but for concealment they are the exact same the rough texture of the grip may chafe more on the G4.
Of the two pistols the OP mentioned, the Gen4 G30 will be better suited for a smaller hand. The Gen4 G30 without a back strap adapter installed has essentially the same dimensions as the Gen3 G30SF (Short* Frame), but the Gen4 "feels" smaller in the hand. The G30SF has deeper texture on the back strap and finger grooves, whereas the Gen4 texture is uniform around the entire circumference of the grip. The net effect is the Gen4 is a slightly better fit for smaller hands given a choice between these two models.
The big advantage of the Gen4 over the G30SF for shooters with short fingers is the larger Gen4 mag release which extends to the back and is easier to reach with the thumb.
* SF=Short Frame. The Gen3 G30SF differs slightly from the standard frame Gen3 G30 in that the trigger reach is shorter
by ~2-3mm measured from back strap to trigger and depending on how the caliper is positioned. However, the width of the grip at the widest point (32.5mm) is the same for Gen3 G30/G30SF/G30S and Gen4 G30
Google site:us.glock.com "short frame" and site:us.glock.com "slim frame" to confirm the meaning of SF