If the rifle was for just very big game shooting I would pick the 416 Remington. But if the rifle was also to be a play around gun and shoot everything from paper, trees, tins of water and from rabbits up then I would pick the 458, in fact I would pick any 45 over a similar case capacity 416.
For those who might doubt the versatility of the 45s, many years ago my only two calibers were a Mark V 460 and M70 in 458. They shots lots of animals but nothing bigger than kangaroos, goats, pigs and emus. Even used them spotlight shooting roos. Of course there was a variety of loads and it would be much harder had it been a 416 Rem and 416 Wby...bullet availability
