D2S is for a projector/ellipsoidal housing.. D2R is for a reflector housing
Different bulbs for different type of headlights, i will say this(changing the subject slightly) I drive about 40k miles a year and have looked at lots of different cars headlights, I can tell you that it has got to be a myth that OEM use 4300k Xenons, I think 5000/6000k are more like what is used, i have 4300k in mine and if you park it up next to a Q7 for example the blue hue is much more visable, this is the same for almost all HID OEM lights i have seen.
i know people say the housing make a difference, but a projector is a projector the optics are almost identical apart from the beam cut offs, i would say OEM is more likely to be 5000k.