acog have a iron / doctor sight + 4x zoom sight. It is so expensive because of it's zoom and optical fiber technology...
EO-tech have it's own holographic technology to reflect the laser onto the window... Same as the HUD display on a fighter jets. It always follow your head when your head moves. futhermore, you cant see the reticle on the otherside of the window.
Aimpoint have a "dot" on the window, it uses LED to projects a LED dot onto the window. Which is crap as i thought.... Because you can see the reticle on the otherside of the window / the LED light. It gives you tunnel vision.
etc....
Go to utube to search How eotech works and you will know why it is good laaaaaaaaaaaa XD