The difference between factory and retrofitted HID systems is that, factory HIDs are designed with the brighter beams in mind. the reflectors or projectors need to be properly focused to produce optimized road illumination as well as to reduce glare to the oncoming cars.
the europeans have laws that require manufacturers to include self-levelling function or headlight washers for HID headlight systems.
Projector headlights produce better and safer results than reflectors when retrofitted with HID.
sadly there are too many car owners who don't understand how these things work and don't know that their headlights are way too intense with their HID kits installed. it's just too freaking glaring no matter coming from the rear or the front.
their ignorance caused the hate on the HID kits
As for how the JPJ boys know? depending on how suspicious your car look i suppose. they do look for ballasts, wiring and stuff like that. For those with whitish or bluish beams, there is no question.