I love Exposure for helmet lights and I have one of their Strada road bar-lights as well, but I’ve been using Lumicycle since the halogen days and, in contrast to the self-contained thing that you get with Exposure – for longer, winter, rides, I really like having the option of simply changing the battery if you need extra burn time or want a back-up in proper sub-zero conditions when burn times drop off due to slower battery chemistry.
Not an issue if you’re only out for four hours or less I guess, and you could, I guess, simply fit a back-up cell / Piggyback or whatever they’re called now, but the latest Lumicycle units are ace ime: stone reliable, great back-up and I like being able to change up and down the light output sequence rather than having to cycle through the whole lot.
That said, the programmability on Exposure stuff is great and I’ve found their customer service excellent as well.