Shotgun is mostly used on short distances, that is why you can see red dot or holographic non-magnifying sight on a shotgun more often than optic sight. Typically, red dot, reflex and holographic sights are designed for fast target acquisition usually within a 100-yard range, which is suitable for both hunting and tactical situations. Many shooting experts recommend that you shoot with both eyes open especially in a tactical situation. Red dot sights allow shooters to keep both eyes open because of the dedicated focusing of the sight. The shooting eye is not strained when using the sight.
A holographic sight on a weapon is a sight that does not magnify the image of the target. Instead, the sight has a glass optical window that the shooter looks through and sees a reticle image that gets superimposed on the target in the distance. Obviously, the reticle isn’t physically on the target, but in the glass optical window, it creates a hologram to make it appear like it is. This allows the shooter to more accurately aim at their intended target and fire at it without trying to get their target in the middle of some magnified crosshair.