tsg... /ubbthreads/images/graemlins/thumbsup.gif
That's about as good an explanation as I've heard/read...
Tactical lights, which are true tac lights, are ones that address a "tactical environment." It basically comes down to combat tactics. If you're going to engage a hostile target in a low-light/no-light CQB environment, then you'd better have a light that's up to the job, including its use in handgun flashlight techniques, such as the Harries/Ayoob/FBI/Rogers-SureFire/Chapman/etc.
A high intesity discharge light would put out an intense amount of light that would obviously be blinding to an armed suspect, but given its current form, it would be too heavy and cumbersome to effectively manuever. I would correctly prefer to operate in a more tactically sound manner by employing a light such as the two cell G2Z, of course, a tactical light. I can move better with that light, I can identify my areas of threat, I can identify my target, and it's the other half of my force option that's ultimately going to aid me in putting myself into my opponent's OODA loop.
Handgun flashlight techniques is serious business... it requires a serious light tool. If a company chooses to market their light as a tactical component, then it should live up to that standard. But it doesn't always happen that way. Training and the actual application of the light is what weeds out the marketing hype from the real goods.
-Jim