Don't know if I'd agree that Jason is weaker (he flipped a 2-ton car over with his bare hands in the comics. He might be as strong as the xenomorph, if not stronger), but in general I agree with your conclusions. The outcome would fully depend on how many Aliens were involved in the fight... if it was just one xenomorph, all my money would be on Jason. But if the Aliens were attacking as a horde (as they are wont to do, as seen in the films), then I think numbers would win out.

Now how about if a Facehugger got Jason, made a little Jason Alien (I'll call him "Jalien"), and then, once Jason had fully recovered from his entirely fatal injuries (as he is wont to do, as seen in the films), he fought the Alien that came out of him?
Jason vs. Jalien... Now THAT'S a fight I would pay to see in theaters!