I would first heed Kenneth 1's suggestion to try them on for size and take it from there. There is no question the Rigby is the more useful round and likely, the more saleable, should things come to that. I can think of no cartridges I have not fired other than one or three of the Nitro-Express rounds. I can tell you it is best to "work up" to .50 caliber, rather than leaping from .375 to the .500 Jeffery, for example. Generally, the recoil thresholds from .375 to .416 Rigby to .458 Lott to a .500 are very distinct and taking the plunge too early has ruined many a Big bore candidate. Borrow some guns, test the waters .. you'll make a better decision.