Louis-Baer. Baer had just lost (3 months before) to Jim Braddock but previously had scored his 2 greatest wins with one-sided ko´s over Carnera and Schemling (Max would rebound to knockout Louis) so was still close to his peak. Cleveland Williams hadn´t scored any notable wins before Ali and had recently been shot in an altercation with the police in which he was lucky not to die. One of those comeback wins was over Mel Turnbow (6-4 record)-ho dropped him early and survived the full 10 rounds. Turnbow had just been destroyed in a round by a young Joe Frazier (4-0) and would later get stopped by Jack Bodell! His best win was a ko over future champ Ernie Terrel over 4 years before and best performance was probably the rematch split decision loss to Terrel in the rematch 3 years before.
In terms of quality of opposition, Baer was better than Williams who had literally survived a gunshot wound. In terms of how close both guys were to their peak, i would say 25 year old Ali was at his absolute peak while the 21 year old Louis was still developing. Now Louis himself thought the Max Baer fight was his best fight. In terms of offensive ability and speed, this might be true but Louis was still a work in progress defensively and i would say the 38-42 version of Louis was just a better fighter. So if you are ranking the performance based on the quality of the opponent, i will go with Louis since Baer was a better fighter. If you are ranking the performance in terms of ability of the winning fighter, i will take Ali since he was at his peak compared to Louis who was in his prime but not at his peak.
Louis vs. Baer is imho one of the best demonstrations of boxing technique, combinations and timing over raw punching power of all time.
I like Louis vs Baer ... Baer was still young, in his physical prime, had a terrific chin and power .. I love this performance because it's a rare example of Joe using his legs and speed opposed to the classic stalk ... Joe was blazing fast and his punching exhibition , the combination punching was as magnificent as any captured on film ... Ali was terrific vs the Big Cat but Williams was a bit long in the tooth in my opinion ...