Also relatively few tires have a bottle dynamo roller drive strip molded on the sidewall any more. Most Schwalbe city tires do but few others. Without that a sidewall dynamo can be rough on a tire.

BB dynamos had the reputation of being more efficient than sidewall dynamos but I have not seen it quantified. I suspect they disappeared as common equipment in the USA when mountain bikes took over 90% of the market as they will not work with knobby tires. They also require good wiring sealing as they sit in probably the wettest and dirtiest possible position on a bike.

The hub dynamo is almost certainly the most reliable version but it has the major disadvantage of requiring a new wheel be bought or built to install it. The BB dynamo is a reasonably priced alternative IMO for occasional use that I intend to try out.