(Rolls Eyes) Riiiiight, those are "specious" but your claim that "remembering" to come in out of the rain is a problem, or that buying a heat pack for every time you ride to warm up the battery are totally reasonable...

Buy whatever you want for a light. There are some advantages to battery lights as well, like being able to move it between different bikes. But for a light that "just works" on one bike, with no screwing around with charging, batteries, spare batteries, etc, a dynamo light is better.

Your idea of battery lights being better, is from a time when lights weren't very efficient and you needed batteries to get a decent amount of light.

This is an image of a dynamo light from that time - 2008 -


Clearly this is a "be seen and don't ride to fast" kind of light. I wouldn't have bothered with a dynamo hub if this was all I was getting.

But here's an image from last year with a dynamo light (the Cyo - around $100, I own it) -


Here's an image from this year's dynamo light (The Luxos U - $160 to $240 depending on model) -


(Images from Peter White's site - note that it's not greenish in person, it's just a camera white balance problem).

These images are a little brighter and clearer than you'd see in real life - but in real life they're better or as good as my battery lights in actual use as well. In order actually beat my battery lights in real use, I have to run a Sec 900 on high and Seca 1400 on medium - 2 batteries, very expensive, and blinding even for some cars.

If someone wants to be as cheap as possible in the short term while still having enough light to ride with, a battery light is the way to go. If someone wants the least daily-hassle light to use, a dynamo is better.