EDIT: Hmmm... Unless this is "who would win in a fight" thread lol. Then either Ezio or Ratonhnhaké:ton since they have guns at their disposal.[/QUOTE]
If you read Altair's codex, he did, or should have at least had a hidden gun of his own.
In my opinion, Ezio has the best chance as he's always ridiculously armoured and has a crossbow which, whilst not being as fast as a bow or flintlock pistols would still pack a punch and severely injure if not kill Connor and Altair stone dead, saying this, Connor does appear to be much faster and stealthier giving him a significant advantage