How well do they conduct? At the moment aluminium is kind of the "sweet spot" between weight, cost, and conductivity.
Ballistic conduction means 'perfect' conduction in a sense. There's no resistance. It's only for armchair swcnts though. Other metallic swcnts are also great conductors, but if you separate out the chiralities (semiconductors, etc) you might as well separate to just armchairs.