Judson:
If you intend to impress others, then the .475 No.2 is undoubtedly the most imposing cartridge of the three listed. Its just such a big sucker!

My own preference might well be the .577 x 2 3/4 in the 650/90 configuration. Manageable recoil in a 10 1/2 to 11 lb gun, and with Woodleigh bonded-core bullets, or their new 650gr steel-jacketed solid, it's a far better cartridge today than it ever was, a real giant-killer!

The full-nitro .500 needs plenty of gun-weight IMHO, difficult to build into the action of a converted shotgun and still get the handling right.