I disagree with most of above. I shoot Bullseye and Steel bowling pins. The folks with red dot sights do better.
Most of my hand guns have red dots. After a while, I can pick up the gun with my eyes shut, point it at the target and open my eyes. The dot is there. I have had dots fail, usually because a dead battery.
Once you learn to use a dot sight, you will shoot better. Its one focal plane.
Using the dot, you can look at the tarrget instead of the sight. Like throwing a ball (which I suck at) Look where the bullet is going.
I quit shooting Bullseye because the sights were blurry. Now with red dots, I am back in the game and my scores are better than ever.
None of my guns with dot sights have co witness sights. I don't want them. I don't need them, these guns are for games not personal defense. If I had an RDS on a defense gun, then maybe co witness sights, but probably laser grips.
Tube sights (ultradot) are easier to aquire at first.
David