There’s no footage of either guy fighting so it’s not like we can have a clear answer either way, but it doesn’t mean we can’t have some fun with the idea. Goddard, despite being knocked down multiple times by Peter Jackson, did appear to be the fresher fighter by the end of their fight. And I can’t recall reading that anyone else’s strength, aggression and pace tired Jackson like that and that’s in spite of Goddard being the smaller man by nearly 20 pounds. I get that Greb fought and beat many great fighters as big as Goddard and likely as great or greater of that size but did they have that combo of relentlessness, a stupidly high pace even into late rounds, toughness, strength, recuperative abilities (Goddard did have a solid chin but it got cracked by better punchers like Jackson and Choynski yet still came back stronger) that Goddard had?
Firstly, Goddard KD'd Jackson in the 5th. Secondly, I don't think Jackson outweighed him by much at all. Thirdly, Goddard stopped Choynski twice and Peter Maher, also, whilst in his prime. Once the drink began taking its toll about 1897, he hit a giant losing streak.