In my opinion, McCall would have beaten Rahman because of his far sturdier chin and superior power. Yes, I believe that McCall was clearly a harder puncher than Rahman despite the fact that Hasim has better KO%. McCall showed his power not only in the fight against Lennox Lewis. He also KOed Oleg Maskaev (unexperienced but still) wit a single punch and brutally KTFOed Henry Akinwande with a single punch. While Rahman never KO'ed any top-100 HW other than Lennox Lewis with a one punch. He landed incredible amount of power punches against Corrie Sanders and Kali Meehan and they were still stopped standing, he couldn't stop Obed Sullivan, Monte Barrett, shot versions of Trevor Berbick, Jesse Ferguson and Alfred Cole. And, hell, even glass-jawed Oleg Maskaev took Rahman's punches very well in BOTH fights.
Rahman at his best was better than McCall at his best. McCall may have been more consistent though. So, assuming best vs best, Rahman on points.
Actually, going over their records, scratch that. Rahman was flat out better than McCall. For the guys ripping on Rahman's punching power, consider that McCall went the distance with: Sinan Sanil Sam (whoever he may be) 27-3 Marion Wilson 12-40-4 Cornelius Ellis 7-9-1 and he only just managed to beat the mighty Sedreck Fields 10-10 by SD. Rahman by UD.
Depends on the shape and motivation of the fighters. Assuming both are in shape, I think Rahman on points is the most likely outcome. McCall was not a boxer, and has zero UD wins over top fighters. To win here, McCall needs a knockout.
Rahman was limited by guys who smothered him like Ruiz and Holyfield. Guys who stayed at range with him generally lost or stopped him late while trailing. Rahman would be a slight favorite but McCall did do away with Akinwande and Damiani fairly late.
if Rahmmy hits Olly hard enough to wake him up, Olly will pep up enough to win on points SD. Otherwise, dec to Rahmmy.