There are five kinds of Halogens (Bromime, Flourine, Chlorine, Astaine and Iodine), Bromine is the most common now.

Halogens are inefficient! They are very expensive to operate, especially considering the lumes to watt ratio is very low.

Really the only two choices in the HID lights are MH and HPS. They really don't cost so much considering the huge returns.