It's a pretty decent difference in my opinion. Primary ones for me were the grip and mag release. All Gen 4 Glocks with no backstrap are the equivalent of the older SF (short frame) models. Shorter distance from the trigger face to the back of the grip. The flatter magazine release and extending it rearward in the grip solved the issue of having to slightly rotate the gun to get good bone on button contact to ensure a clean release. Another nice improvement is the dual captured recoil spring, not that there is a ton of recoil anyway, but I believe it helps. Especially noticeable in the G42, which is the nicest shooting .380 I've ever shot. I shot Springfield XD9's until I picked up and shot a Gen4 G19. That was it. Unfortunately I lost quite a bit of $$ in the transition from xD to Glock (custom work, holsters, magazines, you know how it is....). Well worth it in the long run though!