What has been omitted from this discussion is that headlights and especially the upgraded versions really need motor driven units to dynamically correct the beam. If there is no facility to control this they can be a nuisance and not the cheap and simple upgrade they seem, moreso in short wheelbase cars .
My previous modern (2004) with halogens had a dial on the headlamp switch so that the beam could be adjusted remotely to suit if you were unloaded/loaded or pulling a trailer.
My current modern (2013) has Xenon lights that are motor driven and dynamically respond to the movement of the car via a range sensor and 3 suspension sensors - NSF OSF and 1 at the rear. This year all 3 have failed one by one at a cost of £200 each inc labour ! Sadly, when the sensors fail, the headlights instead of defaulting to a mid position just point straight down which is like trying to drive with sidelights. The way forwards is backwards.