Spino is only bigger because of his sail.
If you're referring to the actual species of Spinosaurus and not the Jurassic Park version, that actually depends on who you ask. Spinosaurus, even with the controversial newly described posture and rear limb size, was likely longer, heavier, and overall more massive than T-Rex. If the new hindlimb size is true, Spino may not have the T-Rex beat in the height department - but otherwise it was probably the largest land-dwelling carnivore to walk the earth (that we know of.) Current estimates put it between 49 and 59 feet long (depending on which scientist you ask), 14 feet tall (including spines, I believe), and a weight between 12 and 20 tons. On the lower end of that range, it would have been bested in size by Carcharodontosaurus and Giganotosaurus, but if the average estimate is accurate, it exceeds them.
For comparison:
Tyrannosaurus is estimated to be up to 40 feet long, 12 feet tall, and 8 to 14 tons.
Giganotosaurus is estimated to be up to 42 feet long, 13 feet tall, and 4 to 14 tons.
Carcharodonotosaurus is estimated to be up to 44 feet long, 12 feet tall, and 6 to 15 tons.
Spinosaurus is estimated to be up to 59 feet long, 14 feet tall, and 12 to 20 tons.
I don't think the current estimates on Spinosaurus should be taken as fact until a complete specimen is found. As it stands, only fragmentary remains from multiple specimens of varying ages/sizes have been found.