Spinosaurus - fisheater, Tyrannosaurus - designed to kill big animals. The answer would be obvious. Anything put against a T-Rex just doesnt stand a chance, not cause I think T-rex is awesome (im sure all of you think that its awesome as well), but because there is enought evidence to show its real strength, which is even greater than it was thought before
I was wrong, the "most recent" bite force estimates, which show the higher value than before were around for a long time now, so it isnt actually recent. Although still proves my point
I think the Rex would win out of the sheer fact that it had a stronger bite-force, lotsa muscle. Just because something's bigger doesn't always mean it's going to win out.
2: it was a juvenile