scubanarc once bubbled...
As for light heads, there is no perfect one out there yet. The most reliable light heads out there right now are the non-focusable ones because of the way they are put together. The bulb plugs directly into the ballast which makes for a solid connection with no chance of arking plus the bulb is being protected by 2 lenses. The focusable versions have 2 regular wires about an 1 and a half inches long soldered to the posts of the bulb then the other ends are just pushed into the ballast sockets. Which tends not to make a tight connection between the 2.
The focusable ones are the most preferred though, because of the nice tight beam they can produce which makes them great for signaling.
The non-focusable light heads can be purchased with 2 different reflector type's. 1 is the 6 degree reflector and the other is the 12 degree reflector. 6 being the tighter beam but even the 6 degree will not be as tight of a beam as a focusable light head.
So far no one has perfected the HID light head but their getting there.