I don't want to sound like a broken record, but we have a very clear idea what Max Schmeling was, while there are a number of plausible interpretations of John L Sullivan. There are plausible interpretations of Sullivan who could beat Schmeling, and there are plausible interpretations of Sullivan who would be out of their depth.
Schmeling would likely struggle with every interpretation of Sullivan, even the 'untechnical bar room brawler' one. Max was a notoriously slow starter compared to the fast out of the gates Sullivan
