What ever you shoot best.
Seriously, I have never
seen the need to have adjustable sights on a Glock. I hunt
with a Glock 20SF, with a 6" KKM barrel, and am plenty
consistent out to 50 yards, with the night sights I
installed. I am not a fan of the plastic sights that come
on stock Glocks, but other have no problems with them.
As for adjustment, I have never had a need for a vertical
adjustment on my Glocks, but occasionally I have drifted the
rear sight right or left a tad, to tweak a pistol to my eyes.
Squeeze