Versus each other, or vs the typical plane set encountered?
In either case, I'd give the nod to the cat over the jug, even in a slow speed knife fight. The cat simply has more power to play with at slower speeds, even tho' the jug has a higher top-end. The real limiting factor is their respective ranges - the jug has more useful loiter time when upping from an airfield. The jug can also kind of escape from more enemies (ha, ha, right?) than the f6 - that top-end.
Having said that, I'm more a jug driver than a kitty.... I simply never could get used to it. Probably an avoidance response since coming from air warrior my two "rides" were the f6 and p-38, neither of which I could quite get comfy with in here. (Rudder pedals are helpful with 38's and I never bothered to re-hook 'em up for AH.)