Trick question...The Ali opponents were better skilled but the guys Louis fought out of these choices were harder to defeat.
How do you figure? They all lost a quarter of their fights all together. Baer, Carnera, and Schmeling did much better than them. The 3 guys on Ali's resume never even came close to the title.
Archie Moore had some guy named Marciano down in a title fight. (but one month before his forty-sixth birthday, Moore was knocked out in four rounds by twenty-year-old Cassius Clay on November 15, 1962, in an obvious "set-up fight" for Clay).
Its a bigger question than you think Take into account what they would be like if they were active now with sports science and nutrition Some of the old boys would have been unstoppable almost freaks of nature in 2018 Image an 18 year old Mike Tyson properly managed today under Eddie Hearne trained by Adam Booth ,Dom Ingle or Jimmy and Mark Tibbs and backed up at loughborough university. Apply this theory to Ali /Frasier/ Henry Armstrong (Not Lance !) or Joe Luis
The Moore that Ali fought was not close to the Moore that Marciano fought. Not that Moore has anything to do with this thread...