I like the MagicShine simply because I like their taillight too, and with a $2 Y connector I can run both off one battery. You won't find a better taillight for the price ($30).

I have an old MagicShine 900 - I guess 2 or 3 years old at this point, and I don't even use that at full brightness most of the time, For me, the tail is just as important if not moreso, because I ride at night on high speed rural 2 lane rural roads.