...
So, basically it is safe to say the 7970 is solidly more efficient, but not a quantum leap. Fair?
Well a quantum leap is the smallest possible change, so... it's a quantum leap

Honestly, for mining I'd prefer 5970s. At least until we get 7990s.
What's somewhat surprising is what a power hog a idle 5970 is, didn't quite expect it to be *that* bad.