Back to the original question, difference between bottle and hub lights ...
In building my winter commuter bike I am thinking of adding dynamo lighting, and am interested in trying a new bottle style dynamo like the AXA HR (to test the waters without committing to a new wheelbuild). I live on an unlit country road and need a relatively bright headlight so I'm looking at the newer B+M high output lights. Are there different lights for hub dynamos and bottle dynamos or are they all interchangeable? I think it would be smart to buy good lights and if I feel the need to later upgrade to a hub dynamo, but I don't want to fry some expensive light because I used it with a bottle dynamo.
Usually the lights that are made for bottle dynamos do not have a switch because you can disconnect them from the wheel to turn them off. I picked up a couple several years ago on a clearance sale, I used them on a hub but with no switch I just left them on. I later bought a lamp with USB charger, thus no longer use teh old bottle lamps.
If you might buy a hub later, you might want to get the lamp now that has a switch to use with the hub later. But, since I can't feel any drag from my hub, I often just leave the lights on since it will not hurt anything.
Or, since the lamps get better and brighter every year, buy a cheap one now and a better one later if you buy a hub later.