Yeah, aluminum is a worse conductor so you need thicker cable. It's less dense, though, so I think it usually comes out as being lighter. Thicker cables can be more inconvenient. I think aluminum also tends to have more problems with oxidation causing too much resistance at electrical contacts.
I think for motors generally you just end up with a larger motor for the same amount of power.
I think for motors generally you just end up with a larger motor for the same amount of power.