You can say the same when putting HID into a halogen light. Not a proper housing and performance will suffer. The new gen of LED headlights do work well. Also the auto manufacturers have gone away from HID in favor of LED for the headlights.
One thing that kept me from trying HID in my Pathfinder was I would have to give up the high beams and that was not acceptable for me because until last year, my truck had to pass an annual safety inspection to be licenced for operation on public roads. High/low beams were a requirement.
A friend of mine who went LED in his Tacoma a few years ago said they were better than the HID's he had in it before, until the first big snowstorm, then he found that his headlights were too cold and wouldn't melt the snow build up on the lights. Me, my lights don't seem to ice up.