There does seem to be an odd schism between some dynamo hub users and those that swear by battery lights and are certain that a dynamo solution won't work for them. There is a bit of dynamo evangelism for sure. I certainly have it. Once you've 'seen the light', you can't help but start knocking on people's doors and spreading the gospel. I think some of that strong advocacy comes from past criticisms of older dynamo lighting technology. Whenever I tell people about my odd obsession with dynamo lighting they almost always reference the bottle dynamo they had on their old clunker. It's even been parodied in The Simpsons.

I have a friend, a cycling nut who custom builds everything, who scoffs at the idea of putting a dynamo system on any of his bikes. It's just not for him. Fair enough.

With respect to off road riding, Supernova makes dyno powered lights for trail riding and sponsors downhill teams, so they must be doing something right.