We have a dedicated forum for all electronic stuff, including lights, so I'm moving this thread there (from General Cycling).

Mod hat off now, many people use "normal" flashlights as bike lights. You can buy a cheap flashlight mount for the handlebars from various sources if needed. Bike specific lights are designed for that use, they may have more functionality, shaped beam, big battery that fits bottle holder (with long enough wiring), better protection from the elements, better mounts, adjustability etc. Whether or not you are willing to pay more for any of that is, of course, up to you.

Usually the first question when considering bike lights is, do you want to see, or just be seen? Many people ride in places where there's plenty of ambient lighting when it's dark, so they only need to be seen. But if you ride your MTB in the trails, you will need all the light you can get.

--J