I carry a gen 4 Glock 22 in an owb holster. Spare mag weak side. If the size of full frame does not put you off it's a great carry piece. I have no experience with the gen 3. The gen 4 has been flawless for me.
My Glocks are all Gen 4 because I'm a lefty & can reverse the mag release. The interchangeable back straps give you grip options. In gen 5, I am hoping for an ambi slide release. That would be awesome.
Yea though I walk through the valley of the shadow of death, I will fear no evil. My rod is a GLOCK and it comforts me