Since we have no example of Harrison losing to an opponent under 6' and 200 lbs - I don't see, how we can conclude, that he would lose to Burns
He wouldn't beat Johnson. Hart doesn't deserve a Top 2500 rating for head to head. He's probably on par with Bobby Crabtree in that regard.
He never fought someone like Burns either. Based on this logic, I don't see how we can conclude that he would beat him either.
How can you possibly conclude that? The only things that you know about Hart are his record, tale of the tape, and approximate style!
There are significant problems with picking both of them, but you have to do the best you can. You have one man who is big, but never beat anybody approaching world class. You have another man who is exceptionally small for a heavyweight, but had considerable success at world level. The lesser evil seems to me to be to pick Burns.
I think that we have consensus that he was one of the weaker lineal heavyweight champions. You probably don't need to sell anybody that. Having said that, whenever any historian seriously looks into him, he seems to gain ground! I once asked Adam Pollack, which of the fighters that he had researched, had gone up or down, as a result of his research. He said that while Jim Corbett had gone down, Marvin Hart had gone up!
Top 25/30? The article has a different version of the 1st O Brien fight to Box Rec's .Here is theirs. The Philadelphia Item gave the newspaper decision to O'Brien. Hart was down and nearly out in round five but came back to floor O'Brien in round six.. This seems to contradict the assetion that Hart had a good chin as O Brein was no hitter. Its also interesting that Hart's wins are over smaller men or those past their prime such as Ruhlin,Goddard,Choynski who qualifies on both counts ,Root and Maher. Hart has one top win, a highly controversial decision over Jack Johnson .His others are over middles and light heavies,or scrub heavyweights. He doesn't make my top 40 at heavyweight , does he get in yours?
Corbett had always been overated imo.Hart was a decent mauler, but not a great fighter and his record proves it.imo