My take is the opposite of Kraigwy's. Lasers don't do much for me beyond their novelty value. Weapon mounted lights are good juju.
You didn't indicate why you were considering an "add on." To what purpose are you considering putting something on your gun? Recreational or tactical?
Yes, somebody can shoot at the light, but you don't turn it on until you are ready to shoot, or not shoot, depending upon final threat identification. And this isn't a choice between a weapon light and a hand held light. You need both. (Two is one and one is none). Clint Smith wrote about this quite recently in Handgunner, IIRC.
For home defense a weapon light is superior.
The United States Marine Corps: Providing the enemies of America the opportunity to die for their countries since 1775. Semper fi.