I prefer the small halogens to the small LEDs. The halogens cast a wider light pattern, which is a plus and a minus. The LEDs are a lot more visible from far away, so if visibility is what you're concerned with, go LED. However I wanted a general-purpose backup light so I wanted it to also help me see where I'm going. The LED lights are NOT very good for that in my experience.
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Treasurer, HHCMF Club
Now living in the land of the cheesesteak.
But working at a job where I can't surf BikeForums all day any more...