This guy has some comparison photos:

http://www.peterwhitecycles.com/lightingsystems.htm

I wish somebody would give him one of these to compare:

http://lightonlights.com/

That's what I bought, and it works for me. I supplement it with a Blackburn Flea on my helmet when I need the light to see, so that I can see where I'm looking, not just where I'm going.