You have to assign a setting and weapons to make for a plausible thread, else I have to close this. Rules are rules.
I think Leatherface is being underestimated here. He was pretty fast, & he's the same size as Jason. I'd think that in a fight without weapons he would be able to hold his own. The main advantage that this Jason would have over Leatherface is intelligence. He's a lot smarter, so when the weapons come into play, he's going to take it easily.