Jaws has a lot of high end durability feats like falling out of a plane and survive, stones crashing on him, beating a shark straight out. But then he also has enough goofy moments to undermine it.
The Mountains strength is actually pretty overwhelming. He legit ripped a Sparrows (Faith Militant not the animal) head off and also was able to squash Oberyn Martell's head like a grape fruit while he was pretty much dying.
The other big advantage the Mountain has in the books is that he can cover himself head to toe in extremely heavy armor that no other man can where and still functionally fight in it. That presents a huge issue for Jaws. Also sword combat, I can't see Jaws surviving a sword thrust in his chest.