All depends for what you want to use the lights.
LED's have now the Cree Luxeon wich is very powerful and practical when placed on a small flashlight such as the Fenix.
Those little Fenix's will have several settings, you can use the light at 20 lumens or 40 or more up to 140 lumens, also strobbe, and SOS settings are available.
A little light like that can serve well in the house for most chores and will extend to walking the dog or following a path in the woods at night.
Due to the small diameter lenses the maximum throw is about 26 yards, they are very flood light.
When you want to illuminate something a good way off, the High Intensity Discharge lights are preferred for Search and Rescue or border control.
But the are not flashlights! a HID start slowly building power and take quite a few seconds to attain maximum power, moreover, some of them make noises when working.
Hardly what you will use for "tactical work".
NEW GAS INCANDESCENTS
XENON is a gas that will make that filament from the incandescent to be brighter, Surefire was the first user of this gas, and paved the way for all the others tactical lights to follow.
HALOGEN is often find in Xenon bulbs as is the gas that recycle the metal of the filament, back into it, without HALOGEN a pure Xenon bulb will soon be black from metal deposits on the glass envelope.
Are the ones that I use in the BOREALIS and others Black Bear lights, they are not flashlights bulbs at all, but used in medical instruments, they sport two or more of the above gases and are subjected to a lot of internal pressure to work more efficiently. The inside temperatures of the super-bulbs is about 6,000 degrees at the filament.
That is why they are capable of 1050 lumens of light when stimulated by a 12 volts system.
HIGH CURRENT NIMHS BATTERIES
Are as important as the bulbs, also new improved Lithium Ion batteries are showing up in the market, that have also high current capabilities.