Basically, you can have low-powered torchlight or high-powered ones. It depends on the type of bulbs (for incandescants). Krypton bulbs usually will have longer run-time, this is the 'not high drain' type of lights. Krypton bulbs gives "yellewish orangy beam". There is another type of bulb which will eats up your batteries like nobody business, these are bulbs that use xenon gas. Surefire torchlights is one of those that use xenon throughout its product line. See
http://www.surefire.com/maxexp/main/co_disp/displ/pgrfnbr/16/sesent/00 . These xenon bulbs are damn bright and put out "white" beam but downside is run-time is low, typical run-time is only 1 hour on lithium batts, yes, lithium. These are the high-power, high drain light. Of cause there are also xenon mixed with halogen, long run-time xenon and other types of bulbs beside the 2 types mentioned here, but generally these are the 2 common types found in the market. For the LED scenerio, those 3mm and 5mm array flashlights are the most power saving and Luxeon V LED are the most power consuming LED but the brightest LED you can find.