What is stronger giganosaurus or spinosaur?

It is impossible to say for certain which was stronger because the only remains we have of either of these creatures are fossil bones, and even a nearly complete Spinosaurus skeleton has never even been found.

Giganotosaurus was 40 to 43 feet long and weighed between 6.5 and 13.8 tons, not to mention it had the largest skull of any known theropod. They were adapted to hunt large dinosaurs, possibly even sauropods much larger than themselves.

One of the relatives of Giganotosaurus lived in packs, and if Giganotosaurus did, too, it would have a huge advantage in a fight against Spinosaurus.

Spinosaurus, on the other hand, was 49 feet long but probably weighed between 4.4 and 9.9 tons, but possibly as much as 18 tons, according to various weight estimates. Even if it were larger, though, it was almost definitely weaker than Giganotosaurus. Spinosaurus was adapted for hunting Freshwater Fish, and its jaws and teeth weren't powerful enough to kill dinosaurs as big or larger than itself.

Thus, Giganotosaurus was almost definitely stronger than Spinosaurus.

Although both Giganotosaurus and Spinosaurus were around 97 million years ago, they never would have encountered each other, because the former lived in South America and the latter in Africa. The two continents were already separated by the Atlantic Ocean by the time these two dinosaurs existed.