Easily Lewis. Lewis was toying with Rahman and laughing at him literally all the way to being knocked out. In addition to that embarrassment, Lewis was supposed to reveal his skills to a new crowd in Africa. Wladimir on the other hand was serious all the way yet stunned and confused by what his opponent was able to offer, specifically the speed. I can't see how any reasonable or logical person would pick Wladimir over Lewis in this case.
Pretty embarrasing to be clowning a guy one minute, and then getting caught flush and out the next. Still, the revenge KO was devastating and made it clear who was better. Wlad kept getting up, but got starched repeatedly and had his major flaws exposed. So, you either pick a guy making a stupid mistake and paying for it, or a guy who was just plain steamrolled while taking it seriously. Considering the massive KO Lewis layed on Rahman in the rematch, and the fact Wlad never avenged and was forced to reinvent his style directly because of that fight, i go with Wlad, barely.
Wlad was a bloody mess that kept getting KD embarrassingly and was rolling around the canvas like a ******. The Glass was knocked down while attempting to clinch by a 40-1 underdog. This prompted him to hire Stewart and completely change himself. And Rahman was a live contender at the time ... he wasn't retired at the time and he didn't take the fight on short notice.