Both Glock generations are nice, the Gen4 gives you the interchangeable backstraps so you can adjust the grip to fit you best compared to the 'one-size fits all' approach most firearms have (Some Glock models have a short-frame model in Gen3) and they have dual recoil springs that you only had in the sub-compact Gen3s. However, like was mentioned above, the Gen4 Glock finish is much rougher for an improved grip and possible expense in everyday comfort.