If an intruder is willing to ignore my dog barking @ him in my house, he's not going to be worrying about a car horn blaring. They already know just about how much time they have to do the deed they want to.
If he gets far enough into my house to set off the 300 watt strobe pointed down my hallway attached to a motion sensor, he'll never know what hit him as he's falling to the floor in a crumpled heap.
Have you seen the LED multicolored dazzlers? Forget the strobe, this thing will mess you up even when you know what to expect. I was trying to find a link earlier. I saw them out at a security convention earlier in the month.