I still have and use my 2 original 6P's that I got when they were first introduced. I have been a confirmed SureFire user ever since.
The 6P is now a whole family of lights, handheld and weapon lights.
Factory bulbs in incandescent and LED as well as aftermarket bulbs, allow the 6P "series" as I call it erform just about any task that a small light would be used for, excet when you need a low lumen otion or a one 123 battery compact.
For ruggedness and General utility the 6P is hard to beat.
For handheld use with handguns, the lights with the syringe gri are the way to go.
For a less expensive General Purpose light there are the Nitrolon lights.
There are several models of SF Weapon Lights that use the P60 series bulb.
So, if most of your lights use the same battery and can use the same type of bulb, and you can change from LED to Incandescent, high to lower lumens, ie, pick lamps with the runtime/lumens you need, it makes you life a lot easier, IMHO.
I have more flashlights that use the P60 type of bulb than any other.