Let's get something straight
Jurassic Park Three is a fantasy movie, and so is the fight. Spino now is believed to be a quadruped, because it would be clumsy due to the heavy sail and fall and break its spine. That was a death guarantee. It didn't have strong arms; it had front legs. Also, its jaws were not as crocodilian as you may think. Compared to Rex's strong, deep jaws, they are much weaker and thinner. Also, their teeth are hollow, uncurved, with no serrations; the opposite of Rex's teeth. They were made to hook fish. Rex's were made to crush the horns and frills of its ceratopsian prey.
T. Rex was more muscular of a dinosaur, and also faster. It's got lots of room for muscles in its neck and legs. It can lift up a hippo and then throw it! Also, we know it could run faster because of a muscle connecting from the thigh to the tail, like in crocodiles to increase speed. Yet, it's a biped, so its much faster than you think.
Also, its little arms are short but not weak; they were estimated to be ten times stronger than the arms of humans. So if it fell, it could pop back up fast. Also, they were armed with sharp claws that could pierce like raptor claws if prey was close enough. Since spino wasn't taller than Rex, its neck would be an easy target.
All Rex had to do was push Spino over, and/or bite down onto its head or neck. Its 12,800 psi bite force would just finish the competition. T. Rex would win ninety percent of the time, so its still king. If you can't see this, I feel sorry for you.