The difference is the Point Blank Range or “Combat Zero” changes as sight height increases.
If you take an extreme case it’s easier to see. When you separate the sight line origin from the bore line origin by several feet, the angle between the sight line and the bore line would be larger to zero the sight, it would result in only being able to make the parabolic arc of the bullet path cross the sight line once, not twice as is common with lower sights, for instance the AR15 zeros of 30m/300m, 25y/300y, 50y/200y, etc, as the bullet rises above sight line and returns to sight line.
If pistol sights are high, you’ll have a wider range between the bullet crossing the sight line, increasing the “combat effective zero” distances provided the bullet is moving fast enough. But as consequence, the sights are actually inaccurate over the distance between the two sight line crossings to some degree.
If you zero for the distance you’re shooting for score, it never matters what your sight height is, provided there is no obstruction of sight picture.
40s&w 185gr at 900fps, vital zone 5in, zero at 25y, drop table shows at 70 yards to get the end of combat zone drop, 66 yards if shorter sight height, it’s basically not a pistol-range relevant phenomenon.
Andrew - Lancaster, CA
NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / NRA-ILA contributor, USCCA member