A projector does what it sounds like...project light in a focused beam. By doing so it reduces light scatter by putting the light where you "aim" it. As opposed to a reflector housings that simple "throws" light in any direction without the ability to "aim". HiD's in a reflector housings will look bright and be bright but throw light all over compared to a projector housing. No bulb, in a reflector housings, can be "adjusted" to match the "throw" of a projector.It really doesn't matter whether it's a reflector or projector... if the LED replacement is designed to match the placement and orientation of the filament of the halogen bulb then it will work equally well in a halogen reflector or a halogen projector. After all, they don't have different halogen bulbs (e.g. H11 reflector vs H11 projector) for use in the different types of lamps.