Either will do the job identically.

The 458 is a bigger calibre and will score points with your buddies in that regard.

The 416 Rigby is the timeless classic and is even known to some non gun owners who 'know a few calibres'.

It will come down to whatever you feel out of 'Size versus pedigree' gives you the biggest hard on.

Personally I would choose a 416 rigby because it can be loaded for long range shooting.
On the other hand the 458 lott can use cheap soft 45-70 bullets so you can do more plinking etc. with it.

Karl.