Uh... no, we don't go by mechanics. There have been several cutscenes, novels and cinematic trailers that show what each assassin can do. Ezio and Altair have both done the whole "four man counter takedown" thing before, just outside of gameplay.
Personally I think Altair takes this, if only just. Being raised as an assassin from birth (unlike Ezio, who was just a pretty tough guy for the first 18 or so years of his life, and Connor, who was more of a hunter than anything else until he reached the age of 15 or so) gives him an advantage. Another thing to consider is that he had a lot less to work with in terms of tools and weapons than the other two. Both Connor and Ezio had firearms, while Altair had to rely on blades alone. Feat-wise, I think they're all pretty much even. All three men have shown amazing adaptive fighting styles, what with their habit of charging in with their fists and using enemies' own weapons against them.