One need only to strike a heavy bag suspended from a stand or ceiling to see this. Compare the reactions of the bag when you punch or palm strike. There's a more violent jump in the bag when you palm strike. Punches have a primary effect on the target struck. A punch to the head will usually affect the area the knuckles made contact with.
Palm strikes have a secondary effect.
A palm strike to the head won't cause much damage to the contact point, but will have an effect on the neck and usually jars the body. A palm strike done under the chin will often produce a one shot knock-out due to the whip lash effect. A palm strike anywhere to the head area will almost always affect balance, because the strike will take the assailant's ears out of line with his hips. This opens up other parts of the body for combinations or a takedown. The palm strike can be used effectively to the head, body, hip socket and knees.