Can't vote. I use both. Of course I generally use semi-auto for longer distance shots, and full-auto (pfft... right... full auto... it's more like burst shots) for close-quarters.
The only thing I hate about this technique are those times that I haven't run into an enemy in a while, and I have forgot which setting I was last set to. That usually lands me in more trouble than I'd like, but not often, though.