I have undergone serious changes to my Cretaceous world view since learning that Spinosaurus aegyptiacus was larger than Tyrannosaurus rex. Much larger!  Frankly though it's amazing that Tyrannosaurus rex has lasted over 100 years as the world's ultimate land predator even if only to casual perceptions. Like many others I don't subscribe to the Jack Horner hypothesis that T Rex was primarily a scavenger (especially if it was any sort of varient of warm blooded!). The discoveries of Carcharodontosaurus, Giganotosaurus and more recently the re-discovery of Spinosaurus still haven't toppled the idea that T Rex was a beast.

Though politically uncorrect an analogy to dogs bred for fighting may be apt when comparing the advantages of the different predators in regards to their size specifically. Jack London's White Fang demonstrates the advantages a strong, short bulldog can have over the larger wolf; stemming from those imageries I have convinced myself that a Spinosaurus would not be winning a no-holds-barred cage match with a Tyrannosaurus rex. So let Apollo Creed be the new fan favorite, I've still got my money on Rocky "T Rex" Balboa.