Hi Brian, if you've got young good eye's use the iron sights.
However if you're like some of us on here who have lost the razor-edge of youth you need an optical sight.
Rough guide, Red Dot for speed shooting and reasonably good, but for pin-point accuracy use a scope. Slightly slower target acquisition as you tend to notice every little movement of the pistol.
Personally, Red Dots every time
atb Phil