The Speer Reloading Manual #14 lists reduced loads for their 235 grain "Hot Core" .375 bullets. These are available at less than $20 per box of 50. They are very easy on the shoulder to shoot with 28-30 grains of SR 4759 powder.

Bottom line: Go with the .375 H&H. It is a much more versatile round than the .458 Win Mag.

The 375 is more versatila and maybe a more practical hunting rifle. On the other hand a 458 might be more fun for a plinker. Cheap bullets can turn it into an offbeat sort of plinker. Our crew had a few competitions flinging 405 rems in a very mild load at preposterously long ranges. Going to try that again someday.