I like a headlamp for doing stuff around camp when it's dark. I also like a headlight on my bike that will always be facing oncoming traffic, no matter where I'm looking. If the batteries run out in one, I can use the other to change the batteries in the first. The weight of either light without batteries is negligible, so if you're going to carry more than one set of spare batteries anyway, you might as well carry a spare light.
LED over incandescent without question. More dependable, more efficient.
Wide beam over narrow beam. It's more important to be seen than to see.
Batteries over dynamo. It's good to have a light that you can use off the bike as well as on the bike (see above).