Originally Posted by StephenH

There's not any one easy answer.
What I found several years ago was that the lights powered by 2 AA's weren't bright enough, the rechargeable ones didn't last long enough, so for my first 400k, I got a generator hub and light and have been using it ever since. I didn't try any high-dollar rechargeables, so there may be other options, but I couldn't afford to try everything out there, either.

One problem is that it's hard to judge adequacy of lighting from internet pictures or looking at lights in a store. If you're doing some sort of organized ride, try asking other participants what they're using. If they live close, see if you can meet up at night and see what their lights are looking like.

What I found with the Edelux and Son 20 setup is that it works great in the wide-open country. If you're riding around town, with lots of headlights and stuff, the light tends to get washed out in all the other light. If you have it adjusted wrong, it's not so hot, and I've seen people riding with their light set to give them a big dot of light 4' in front of their bike and that's it. Anyway, it's a great setup for randonneuring, and may or may not be best for other night applications. I think one of the ladies in our club is using the same light but with batteries. Peter White has a lot of light info on his website.

You'll also need some sort of headlamp to read cue sheets or fix tires, etc. And those 2-AA lights are small enough to carry along as backups if needed, regardless of what kind of headlight you have.