A dictionary definition can get to the heart of cunning, especially the core of deceit.
On the other hand, I think it's nearly impossible to define intelligence. "Smarter than" as a working definition at least focuses the discussion on the metrics and implicit assumptions. There's Jobs' famous line, "Computers are like a bicycle for the mind," which implies that intelligence has a deterministic component to it. At the same time intelligence seems to describe the indescribable breakthrough moments as well.
Intelligence is sometimes the best part of cunning (or rather execution, without the deceit).
Cunning is limited by its own constructions. Mendacem memorem esse oportet [1] A liar should have a good memory – it requires carefulness that I think is wasteful in a lot of situations. But if you're good at it, chances are you are successful in a lot of other ways too.
Intelligent people often think intelligence trumps cunning. Truth is, cunning people are very, very successful. Don't underestimate them. (I have.)