I ride with a PT EOS, bike version. I actually have two - one on my helmet (or head when hiking) and one mounted on the handlebar. The one on the bike provides maximum illumination for my forward path, while I can direct the helmet mounted EOS wherever I want. This provides plenty of light for urban cycling,but I don't think it has the lumens for nocturnal single track.

Prefer the EOS because it takes AAA batteries, any style.

The newest thing in wheel generators might be the Copenhagen Wheel. So far it is mostly hype, but it might offer something worthwhile. I haven't yet found even elementary specifications for it, including weight....