375 flanged great cartridge and now there is a 375 V-C rimmed. 375 Flanged is perfect for a double to go just about anywhere.

400 H&H, to many other alternatives already established on the market. 416 Rigby would be my choice.

500/416 is a great cartridge, basically 416 Rigby performance but rimmed - lots of penetration.

450 Rigby rimless is a great design but hard to work up reduced loads for if you like to use it for pigs or bear if Scandinavia.

505 Gibbs has the history etc. but sales of ammo shows 500 Jeffery is more popular today and outsells the 505. 505 Got a very limited range of components to choose from as well.