I would post this on the Jurassic World forum, but the LAST thing the JW forum needs is yet again another Spino vs. rex related topic. I wanted SOME place to post my opinion.. so here it goes. I don't care much about what Science has to say, this is my depiction, and I don't intend to change it.
I think Spino was significantly bigger than Rex. I don't know how much, but just significantly bigger.
I think Spino was just a bit lighter than Rex since it had to be able to hunt in water. I believe it hunted on land just as much as it hunted in water.
I believe Spino was much more stronger than Rex with a stronger bite force.
Now, on to the sail.
I believe the sail was the main weakness and disadvantage for Spino. I believe at the end were Spikes, and on the head of Spino were also spikes. The fin, I believe, if damaged would have resulted in the end of Spino. Even a cut to the fin could have lead to the downfall of Spinosaurus.
I think the sail was used to regulate homeostasis in the body, like regulating temperature. I believe the fins of male Spinos were colorful and used to attract female Spinos, like male birds attract female birds with colorful feathers and such. I also think the fin could be used to warn other dinosaurs to back off or to threaten other carnivores competing for food.
Well that's it, feel free to comment about what else you want to hear about my opinion and also feel free to do what most rex fans do and insult me and try to prove all of my depictions wrong!