Though I have not tried the karate chop to the neck I honestly say that a palm strike to the forehead, unless you do it real hard... in the area of hard enough to knock someone out from pain alone if you hit them anywhere, which will probably kill them, will not knock them out unless you do it exactly right and in a actual fight it's hard to hit an exact spot on the forehead due to it's shape. Your chances of knocking them out with that are next to nil and I've tried using this several times... all it did was snap there neck back and disorient them for a second or two.