Pretty well known when they fought that Peter was a shell, but what if that fight happens while he's still got a full gas tank?
Well let's ask the man who fought them both. When Corbet was asked produce his list, he had Jackson and Jeffries as joint number one, meaning that he was struggling to separate them. He fought them both in their prime, or as close to is as you can get.
Giving Jeffries every benefit of the doubt I have seen nothing of him that looks any better than a poor version of George Chuvalo at best. I was trying to rewatch the Ruhlin footage the other night and all I saw was him throwing one absurd looking left at a time in the most telegraphed , amateurish manner imaginable .. between the Sharkey, the Ruhlin and the Johnson film I never seen him throw a two punch combination. His chief skills seem to be strength, chin and stamina .. I've seen nothing else .. Jackson may have been the best heavyweight at least till the time of a prime Johnson
Jeffries always struggled with quick, mobile fighters and Jackson’s among the smartest heavyweights from the period who could move well. However, Jackson liked to exchange and could be landed on and hurt as Goddard and Slavin showed, I wouldn’t put it past an aggressive Jeffries with a take three to give one mentality stopping him at some point. Jackson has the best chance of beating Jeffries compared to the rest of that late 19th century imo.
Interesting matchup between probably the top two 1890-1905. Jeff was at his worst against good movers. as stated, and Peter struggled somewhat, against aggressive fighters, some of them average, eg Fallon, Lynch and Lambert, as well as Farnan and Goddard. Forced to pick, 25 rounds for points, Jackson, to a finish...maybe Jeffries.