Harrison is terrified of being hit. Anytime he is put under pressure, he backs off with bad footwork, panics, and launches hit n' hopes. He was schooled mercilessly by Sprott, who is barely a national level fighter, and saved his career with a punch thrown while sat on the ropes. He is a joke as a fighter, and delusional as a man.
That being said, Haye is not a pressure fighter until he has his man hurt, so the pace may suit Harrison.
Haye has the footwork and skills to avoid big men (his performance against Valuev was a masterclass of boxing), and the power in his jab alone to drop Harrison.
Common sense and history of performance says Haye wins by KO/TKO within 5 rounds.
That being said, history also shows Harrison to be annoyingly lucky, so anything is possible.