It looks like .458 SOCOM, although a more flexible platform than .450 Bushmaster, is slipping and will likely fade even more in comparison. .450 has Hornady and Remington making factory ammo for it, so there is a fairly ready supply, if not cheap. .458 is one of those rounds that is few and far between, and even brass is hard to find.
If you want a wide array of capabilities, .458 is probably what you want. However, I'd only recommend going that route if you are able to find some kind of supply for ammo or brass, and plan on reloading.
If you prefer to have more ammo availability, then you'll probably be better off with .450, even if you plan to reload.