Frames, gen4 on left, gen5 on right:
You may notice that the spring for the slide lock has been changed to a coil spring vs. the older leaf spring. Also the ambi slide lock, and the lack of a third polymer pin behind the locking block. The pin is polymer and I doubt its removal would affect durability much in a 9mm.
Magwells, gen5 on left with cut-out and flared magwell:
Magazine follower is bright orange:
Slides, gen5 on left and gen4 on right:
The safety plunger has been changed to a ramped/sloped one like on the Glock 43. I have read to give a more consistent contact with trigger bar and a more consistent trigger pull as a result.
The recoil spring funnel/hole at the front of the slide is thicker on the gen5. This area sometimes would break on earlier models in heavy use, especially when the recoil springs aren't changed regularly.
Barrels: Gen5 on the left:
The barrel is said to be more accurate, with different, more traditional looking rifling and a recessed target crown. The chamber dimensions are said to be tighter as well..
Muzzles:
The bevel looks nice IMO.
Another shot to show the muzzle bevel.
That's it, no more field stripping for tonight! lol