Some people claim that the smooth reflector gives the light a little farther throw than the textured reflector. I've got an L1D with a smooth reflector, and an L2D with textured reflector and an extra L1 body. Both are Q5's.
To be honest, I can't really tell the difference in the throw between the two reflectors, running them with just one AA. But my urban neighborhood at night probably isn't the best testing ground.
I find the textured reflector gives a much nicer boundary between the spot and the flood. I prefer the textured reflector, but that may be because I've owned a number of Surefires with textured reflectors.
-- Frank