Povetkin convincingly. KO, probably early. HW boxing is unpredictable but my money would be on Povetkin.
What others have said, Povetkin has the stopping power to layout Chisora at some point, and if Chisora is pressing the action it happens sooner rather than later.
Povetkin for me too. He was much faster and more fluid in his prime. You have to be the cream of the crop to beat Pov and that's not Chisora.