I went with the Lupine Piko 3. It is small and very bright. At full power runtime is 2 hours. I usually run mine at medium power and runtime is 5 1/2 hours. Actually full power is 10 watts and "medium" is 3.5 watts and is plenty bright for me. Low is 1 watt and runtime is 19 hours. You can program it to run at .5 watts and it will last 40 hours. I go the optional handlebar mount. It was probably the best buy I ever made for my bike.
http://www.lupine.de/web/en/products...lights/piko/3/