Well, I sort of imagine that your choice would depend on your style of hunting and which theory of killing you subscribe to, as well as the size of dinosaur you plan on hunting.
Now, since real men go exclusively for the large carnivores, we'll dispense with the talk of lesser dinosaurs and get right down to the mighty T-Rex.
Now, if your going after bush T-Rex, an up-close and personal affair, you'll want a .700 NE at minimum, preferably .950 JDJ. For this article Remington has offered me the use of their newest offering, the Orthopedic Special, in .950 JDJ. This handsome rifle is stainless steel and comes with a special carbon fiber laminate stock and weighs in at a comfortable 4 1/2 pounds, and comes complete with a surgeon and physical therapist for your shoulder. My 8 year old daughter described the recoil as comfortable.
Plains T-Rex are an entirely different affair, however. The smaller, sleeker frame of the plains T-Rex, and the extended range at which it is usually engaged usually dictates the use of the tried and true .50 BMG...........
Man, this is too easy. I should be a gun writer!