The 375 is a great cartridge and it can used for a variety of game. I think the 458 is a specialist cartridge and is not really designed for animals smaller than buffalo. I know of course that you could use it on smaller game but truly believe it’s a big game cartridge. The Bullets are designed for heavy and big boned animals. It does an excellent job on what it was designed for. Unless you are planning a safari for such buffalo then I humbly suggest that the 375 is more versatile and more suited to the game I believe you’re hunting. I used the 460 Weatherby on large pigs a number of times driving a 500 grain bullet. It didn’t kill the relatively small game any better than the 270. Overall the 375 is more flexible than the 458 which designed for large and heavy boned animals. So I’d keep the 375.