Mostly in terms of output, they are essentially two C1's.
As others have stated, there is very little difference at low volume levels between the two. But, if you have the room, the C2's provide a fuller sound at moderate to high volume levels.
As others have stated, there is very little difference at low volume levels between the two. But, if you have the room, the C2's provide a fuller sound at moderate to high volume levels.