The following calibers are basically indistinguishable from each other on game:

450 Nitro Express
450 No. 2
500/450
500/465
470 Nitro Express
475 Nitro Express
475 No. 2

There has been an assertion that the 476 Westley Richards is a step up from this crowd because the bullet is 520 grains. And some people say that the .470 cartridges kill better than the .458 cartridges because of the added bullet diameter. Perhaps, but even if true I think the difference must be slim.

Instead of selecting one of these cartridges over another, I would just select the gun that fit me best and was in the best condition, regardless of which of these calibers it is chambered for.