The only thing that is better with the Gen 4's is the all metal recoil spring and guide rod combo. The Gen 3's have that plastic recoil guide rod. But that is a Quick $50 touch from a few sponsors here. Also Brownells. I picked up a wolf Stainless Rod and spring from High cal for my G22 and a EFK Stainless from Brownells for the G17. You Don't need to do this upgrade but from all the reviews i have seen, it just seemed Like the right thing to do. Along with a extended mag release, grip plug and some night sights i won't be doing any thing else to them. A guy has to tinker a little bit.