Usually this question would provoke a good debate of 4 or 5 pages long involving Bell with his 7mm Rigby all the way up to the boys with their big doubles. That might be yet to come. In the meantime just take what fits in your gun bag best.

Now more seriously, if in Oz on the buffalo where it's a bit more laid back style, why not take the open sighted 458, get up close and enjoy.

Can't speak for Africa really but I would prefer a scope for PG and perhaps for threading a longer shot on Buff through some intervening scrub if you can't get close so perhaps a 375. Then again as said here, you could always scope the 458.