Peeps for all the good reasons listed by the guys above. I like a red fire sight on the front and paint the large aperature ring on the peep with red fingernail polish. I only use the screw in small aperature for sighting in. Target aquisition is a snap. Now that I am at the age for bifocals seeing through a peep is easier than focusing on open iron sights.

As mentioned by driftrider your brain automatically centers your front sight to the circle in your rear apature.But another advantage to peep sights is that they are mounted farther back on the reciever of your gun,and this gives you a longer sight plane,which gives you more accuracy than factory mounted open sights.And as stated the Williams company makes very fine peep sights.Your cost on them is around $35 for a rear peep sight