Though it's bad having the two fighting and I doubt they would actually fight each other.
It was a cool add to the film for an action pack film.
Without strife, your victory has no meaning.
Without strife, you do not advance.
Without strife, there is only stagnation.

The Spinosaurus only fought against a juvenile T:Rex.
The adult T.Rex absolutely destroyed, killed and mutilated the adult Spinosaurus aka THE GIANT DUCK with absolutely no effort.
The T.Rex wins! The End! Fact!
I always tell the truth, even when I lie.

Although we'll NEVER truly know who would win in a battle of the two real life giants. As we know they never faced each other as they lived in different eras and T-Rex had the advantage of evolution on its side, making for likely the scariest land creature to ever walk the Earth.
I think
Jurassic World
best answered the perplex of Spino beating Rexy! The Asian scientiest from the first movie clearly states:
Nothing in Jurassic World is natural, we have always filled gaps in the genome with the DNA of other animals. And if the genetic code was pure, many of them would look quite different. But you didn't ask for reality, you asked for more
teeth
.
Isn't it obvious the Spino from JP3 is the PRE-CURSOR to Indominus Rex? Look at how FIERCE it was!!! How it HUNTED the humans almost for sport vs just for food. It was FEARLESSnot afraid of a T-Rex or any other dino on the island. And let's not forget it seemed to be the ONLY SPINOSAURUS on Isla Sornaagain, very much like I-Rex was the only one cause it killed its siblings.
SO YES, ENHANCED SPINO BEATS T-REX WITH EASE! The End! Spino wins!

Im gonna punch you in the cooter, I swear to God!

Spinosaurs where fish eaters

This is from the trivia section,
"The other reason the Tyrannosaurus is not featured in this movie is because the animatronic puppet was damaged at the neck and was too costly to repair. They instead changed the outcome of the Spinosaur vs. T-Rex fight to have the T-Rex's neck broken and Spinosaur win."

That wasn't Rexy. Rexy was the T-Rex on Isla Nublar, in this movie they are on Isla Sorna. Rexy lives to fight another day, and is in fact the T-Rex in Jurassic World.

I like to call the Spino beep and beep because of that beep fight. How dare they kill Rexy!

agreed!

I concur