Re: Night riding and lights
I think for the vast majority of road riders, as well as MTB'ers, battery powered lights are the best options, especially since they let you use the hub of your choice. Battery powered lights are now exceeding 900 lumens, and batteries are dead reliable. That battery powered lights are the go-to lights for 24hr MTB racing says a lot about their capabilities and illumination.
I had a 200 lumen road light, and frankly found it provided less than satisfactory power output, bur today's lights get the job done well. Here's a gallery of one maker's beam patterns.
Very bright they are. Also, as important as it is to have plenty of light for navigating, it's just as important to have plenty of light so that driver's can see you coming from far away. That's why I prefer retina scorching lights.
One important thing to consider when buying LED lights of either sort--battery or generator driven--is whether or not that light is overdriving its LED's. It's well known that LED's typically have a long life, but what's not very often discussed is that life can be reduced dramatically by being overdriven (too much amperage, too much voltage,....). They don't get more efficient if they're overdriven. They're limited from the start by their quantum efficiency (how many electrons it takes to produce a photon). Overdriving them will actually cause them to be less efficient, as part of the LED, the junction, heats up. Also, as their overdriven, they shed more heat, thus the cooling fins you see on so many lights. It's better to find a well illuminating light that doesn't need cooling fins. With damage from being overdriven, the LED's will start producing less light, and the time will come when they won't produce switch on at all. For properly driven LED's, that's not a worry. Properly driven LED's can easily have lifespans in excess of 10,000 hours: that's over 416 days of non-stop light production.
As a happy bonus, properly driven LED's get longer burn times out of their batteries, everything else being equal.