If they fought 3 times i see Jack winning 2 of 3 with Tom taking 1. A big part of this would be ruleset. 1890s 25 rounder with loose reffing? Tom. 1930s 15 rounder? I'll go with Jack more often than not.
Tom out games him with body shots and wins unless he loses it and starts his fouling. On his best night Jack makes him look stupid but Jack was very unpredictable.
Tom overrated, Jack underrated. Tom had Corbetts number, and had a good win over McCoy. Otherwise even with Maher and Ruhlin and less than Jeff and Fitz. A good but short prime. Jack was tough, clever, skilled,hit hard enough, can't see him losing but...
Jack did not have the chin to win this one. Sharkey had the style to eat up quick boxers, see Corbett or Choynski. I'd favor Tom inside 10.