Happend to be on the Glock website tonight, saw that they'd updated the 10mm page to include the Gen4 G20 and G29:
I noticed that the following measurements are different between the Gen3 G20/G20SF and Gen4 G20 (did not check out the G29 as not interested in that):
Length: 209mm, 204mm, 193mm (Gen3, Gen3SF, Gen4)
Width: In mm, same. In inches, Gen4 is .01 inches wider.
Barrel Height: 32mm, 32mm, 20mm (Gen3, Gen3SF, Gen4). I wonder if 20mm is a typo and should be 30mm, or if that is for real? I know almost nothing about firearm design, but, that seems like a significant unpublished change.
Barrel Length: In mm, same. In inches, Gen4 is .01 inches longer. Given the width change above, I wonder if this is an errata on the Gen4, or, was errata on the Gen3s and they corrected on the Gen4.
Unloaded Weight: 785g, 780g, 780g (Gen3, Gen3SF, Gen4).
That's it...just thought some was interesting.