I think the dominant truly cares about the sub, though it manifests in weird ways sometimes, and some dom/mes cop some really weird attitudes about that. Caring, emotionally and care-taking as a task, puts the dominant in a place of vulnerability (chosen and accepted), which implies (to me at least) that a huge amount of power is given to the sub: the power to be desired.

As Denuseri said, the dom/me has more physical power and more control, and that is a different kind of power. Also, the dom/me generally has more will, more force, and more choice. The sub has one big choice- stay or go.

I don't have a good answer to the original question, because I don't think power can be measured like a volume or a weight can. So it is impossible to directly compare one power to another.