What's the betting that the people picking McClellan, are the same that vociferously argue that modern heavyweights are better because they are bigger?
My evaluation of Jeffries has been recorded here, to much opposition. However, I see Jeffries winning by ko after absorbing immense pain and blood, which is usually the way he wins. The other guy tires out because they hit him so many times their arms got weary. Jeffries is too big and strong for McClellans punches to take effect, besides cutting him up. Jeffries KO 25th round. It's a 40 rounder, right?
I didn't claim that they argued that they were better, solely based upon their size, but they clearly see size as being the most important variable.
You didn't mention any other factors. An important factor in this match-up is that a face-first wharfbrawler, smaller than even McClellan, who possessed little science and none of the grooming of McClellan, was able to beat and bloody Jeffries for 45 rounds over two fights. That's a factor I would like to mention.
Fitzsimmons if that is who you were referring to was 36 years old for the first fight with Jeffries. That one wasn't close. Presumably McCllellan would not warp his fist with electrical tape and tamper with the gloves. Mis-match. Jeffries TKO inside six rounds, who averaged 220 pounds in his title defenses, and would probably be close to 230 pounds today. Also height can fluctuate as much as an inch during the day.. Jeffries was reliable measured at 6'1 1'/2" tall multiple times and this is confirmed by standing next to famous men of similar height long after he retired, such as Babe Ruth. People tend to shrink a little as they age.
Fitz was 36 for the first fight. This guy is fully of errors don't take what he says at face value. He's come back form his 3rd ban ( Could be more if you count his alt posters ) with some bitterness. I don't know what he did this time.
I got Jefferies by KO. Too big and too strong for G-Man. Jefferies vs Fury would be a more even match up IMO.