If we are talking the Mugabi that fought Hagler and before, than I say he wins. Hart had huge power, but that was pretty much it. His chin wasn't the best either. If we are talking after Hagler, than Hart by KO.
I think that Cyclone stops Mugabi late, that experience will come into play after surviving some early leather in the first three rounds, then Cyclone lands a couple of hard punches in the mid-rounds, taking over.