With improvements in technology pertaining to powders and bullets, we are able to do more with less. At one time to increase power, the only solution was to go bigger as bullet design had a useful maximum velocity ceiling of 2150 fps. Now we can depend on bullets to withstand impacts up to 2500 fps. If we can get a .375 bullet to expand to 1" with an impact velocity of 2300 fps and penetrate nearly 3', the .500 bullet that also expands to 1" and penetrates to 3' takes a back seat due to the .375's flatter trajectory. The .416 has a proven track record with flat trajectory and good impact velocity, and I would be equally happy with the ballistics of either rifle.
For years I have wanted a .460 G&A - essentially a .458/.375 Ultra. From a short barrel a 500 gr bullet makes 2300 fps. Given what I can do with my .375 the .460 project is on a permanent hold.
Mark Sullivan made an interesting observation when he first acquired his .600 Nitro. He was very impressed with the ballistics of the big rifle, and just knew he could stop the charge of an African buffalo with a chest shot. For those not familiar with Mr. Sullivan he's made an art form of stopping dangerous game charges with brain shots at "blood on the shoes" ranges. Anyway, Mark get his chance, the buff is coming fast and at 5 yards he fires his first barrel into the chest. He says - You know, that buffalo never read the ballistics of the .600 and he wasn't impressed." A speedy second shot to the brain stopped the action at about 18", saving him from a pounding.
Edited to add -
There is a place for the true big bore, and that is when a solid must be used on very heavy game. Because we cannot depend on bullet upset, the wound cavity is solely dependent on caliber, bullet shape and construction and velocity.