I'll base it on my GEN 4 G21, which obviously uses the same frame.
Texture: The new texture is absolutely perfect. Just the right amount of grit, without being too abrasive (I'm not a big fan of decal grips, both granular & rubber).
Grip: The grip size is also better. It's supposedly the same size as the G20SF, but it feels slightly smaller & just feels better in general.
Mag Release: The larger mag release makes reloads easier, and more consistent.
Recoil Spring: Even though the spring rate is the same, the preload of the new dual spring seems to reduce recoil slightly.
Trigger: The stock GEN 4 G21 trigger is the best stock Glock trigger I have ever felt. Very smooth, and a nicer break & reset than any of my GEN 3 SF's.
GEN 3 20LS/20SF/21SF/30SF/23/34/26
GEN 4 17/19/21/34/35