I think Fitz straight away but when I think more about it, it would be a hell of a match up. Two very good punchers(edge to Bob) very clever tactitians(edge to Charley?) good stamina and punch resistance(edge to Mitchell?) Damn most things point to Mitchell but I gut-feel that Fitz would take it by KO.
Mitchell to me is one of the more over rated historical figures in boxing. Corbett blew him out in three rounds. Fitz would win here, likely early.
Mitchells best days were far behind him when he fought Corbett for the title though the fight did generate a lot of interest. Might post some articles later.
Corbett/Mithcell was a bit of a joke. I have faith in Fitz to found the resolve and win later on, but Charlie really could out hustle him if he moved about enough.
I lean towards Fitz, but under London Prize Ring Rules, this fight goes a considerable distance. Mitchell was a good wrestler as well as boxer. Fitzsimmons, though, for being 167 pounds hit like a super heavyweight. I think he would have taken Mitchell on either set of rules, but it wouldnt have been easy.
I like Fitzsimmons, though a London bout might take a while. http://www.antekprizering.com/mitchellstory.html Apparently Mitchell was something of a rough-neck.