The energy cost of a coin mined today I would estimate at arround 30% of it's current worth. That is much more than the percentage needed for printing a $10 bill. I think it es even more than what it takes to mine gold, I took a glance at these numbers some time ago.
But nobody figured out a better and still safe way to design a cryptocurrency yet. The difficulty and cost to mine is what makes bitcoins safe.

If you take all the overhead for reprinting, safekeeping, transportation, fake money and so on into account - my feeling is bitcoins will win.