Lasers are not more efficient than LED. That's a big reason why laser weapons are difficult to make- most of the energy goes to waste heat.
Why are people worried about laser detectors? The headlights aren't UV. The light coming out of the front of the car isn't even a laser- it's, basically, flourescent...just with a different energy source for exciting the phosphers. Good thing, too. Why would you want wide angle headlight replaced by a little blue dot somewhere out in front of you?