I just watched what you have, I think. I didn't see Conn fighting up close that much. I watched Loughran and Walker for a comparison, and Loughran clinched more than Conn, I thought. It is hard to find a fight in which there are no clinches or some infighting, and there would be some with Conn/Jeffries. The arguments given are causing me to lean more toward Jeffries. The point about Conn being able to throw Louis off his game was well taken. Jeff would be knowing what to expect and be going right to the body. Interestingly, the usual criticism of Jeff's opponents--that they were small men--might aid him here. Louis was thrown off by Conn's speed. Jeff might prove to be more used to smaller, quicker men, having cut his teeth on Choynski, Fitz, and Corbett.
The point is that Conn doesn't box some running fight, hoovering points. There are clinches and in fighting in every minute of that footage. Therefore, it's not reasonable to point to that footage as having expectations of Conn boxing and moving as a concrete strategy. Unless one wants to suggest that our Conn tried to keep his distance there, struggled more than he would have against Jeffries.
This takes the Thunder from my 'Charley Burley vs James j. Jeffries' thread. Loughran vs Jack Johnson anyone?
Jeffries never beat a clever boxer who was in his prime, that does not mean he couldn't , it means the jury is still out. I think Louis had a greater variety of punches, better combinations , a terrific jab ,and more correct, and precise power than Jeffries. Jeffries scores big on durability. Whereas Conn troubled Louis on occasion with quick counters, Jeffries would likely not even show that they had registered, but could he pull the trigger before Conn was back out of range? Conn could hit a bit harder than his stats suggest, he stopped a few heavyweights, but he isn't koing Jeffries so he has to out box him. Jeffries is not out boxing Conn so can he wear him down in 15rds? I think Conn could stay out of trouble and steal a points win, but none of my money would be on the outcome. Over 20 -25 rds two scenarios suggest themselves. Jeffries wears Conn down to a walk with body shots,and eventually clubs him down or, Conn turns Jeffries face into steak tartare and either cruises to a points win ,or a tko through cuts.. My pick is Conn by dec , but its entirely possible Jeffries walks him down and puts his left fist into Conn's ribs and out through his back.