I'm going to give the edge to Mr. Perfect here, but in a much closer match than most people would guess. Koloff is a toughguy, and would try to keep the macth as simple as punches and kicks. Mr. Perfect is too smart for that, and would turn it into a mat-based match, where it'll be over quickly.
If Hennig had any issues, he'd have Heenan on the outside to distract the ref, or to get in some cheap shots while he distracted the ref himself.