Plantains and Potatoes--same difference?

So, I recently (meaning yesterday) learned that plantains are known as "potatoes of the air," as well as being in the banana family. It turns out that potatoes (the ones in the dirt) contain potassium in amounts comparable to that found in bananas. This doesn't make me want to start putting chunks of potato into my breakfast cereal, but it does make me feel better about making mashed potatoes for dinner. Maybe we should start calling potatoes "bananas of the ground." Actually, I think the French already call potatoes the apples of the earth...but that's comparing apples and bananas!