Here are some of the factors that you might like to consider (I'm sure that the real enthusiasts can add some more):
- weight
- size
- max output – how bright
- min output – to be discrete
- battery type – rechargeable or not?
- battery capacity – how long will it run (and at what level)?
- recharge – via port or external?
- beam shape – wide and even (floody) or narrow and concentrated (thrower)
- colour temperature – bright white (sort of like halogen bulbs) to off white (like incandescent bulbs)
- colour rendition – CRI (look it up!)
- stepped (how many levels) or ramped brightness
- extras
“tactical” additions (crenelations, tail button etc)
tail stand?
magnet to attach it to things?- cost