What is the advantage of an aluminum driveshaft over a CM shaft? Is the aluminum much lighter? I could see this being a benefit in a light/moderate use car if it is. This would essentially reduce drivetrain loss slightly by reducing rotating weight correct?

 

CM vs. AL i dont think the weight differences would differ that much and rotating mass with a driveshaft is negligible IMO for the avg. 'Joe'
but CM should be stronger and close to the same weight as Aluminum price is probably another story (i havent ever priced a CM or CF driveshaft too an Aluminum)