I agree with much that has been said here.
However, I think that with the criteria set forth, the 458WM is probably the "most reasonable" choice based on availability and flexibility in loading.
As far as rifles available, and most managable in the recoil department, the 458 is the choice.
When it comes to class and capability, the 416 Rigby is the obvious choice for me. It does it all.

The game? Dead is dead, and it wont care if it is a 458, 416, 425, or 404 that did him in. All have proven themselves to be up to the task, so what does it matter? We all have prefernces for a cartridge from Rigby, Westley, or Jeffery, but in the real world, there is no appreciable difference.