well buddy , the function of both is to enhance the night vision , hid is the latest technology (coming in bmw ) and other cars of its class , projector lights as the name suggests r for the enhancement of night vision . apart from everything i think its more of a fancy thing and "shushka" . controlling them doesnt require a rocket science u can control these lights from the light function lever (if they r genuinly installed ) or installed by an expert customized outlet.
diff is of technology , hid is the latest and built in function , projection is a bit outdated now, any how 2 my knowledge both r illegal, cheers!