Princeton Tec's Rage or Tec 40, which is brighter? one used xenon the other uses halogen bulb... i have no idea wats the difference between the bulb types too.
The more significant difference between these 2 lights is that the Tec 40 uses larger AA batteries which allow for higher current and a brighter light. They are both very bright for their respective sizes.
Xenon is one of the inert gasses that can be used to fill a bulb. A halogen gas (such as bromine) can be added to cause a redeposition of a portion of evaporated (read "lost") tungsten back on the filament at high temperatures. This is done to extend filament life. There's a brief discussion of the tungsten-halide cycle included in the write-up HERE.