When choosing a light, consider your terrain, your typical speed, your maximum speed, and how much ambient light is on your route. For instance, my headlight isn't super bright, so I can't safely go more than 15 or 20 mph. I don't mind, but some people will. My path is lit in all but a few places, so see by my headlight's light only a few brief times during my ride home at night. My headlight serves mostly as a be-seen light, except for the times I just mentioned.