As posted above - It depends upon the quality of your eyesight, and the conditions under which you're shooting - and your ability.
Sure iron sights, including tangers, are seen as precursors to modern scopes, but shooting telescopes have been around just as long - at least prior to the Civil War.
"Conditions" include some types of long-range competitions, which preclude the use of magnifying sights (scopes) - like some BPCR events - and lousy weather that might make scope use problematic.
There are no scopes on Olympic target rifles - just peep sights, extended to the rear as far as a tang sight rests.