That makes it a tough choice - has the .450 NE with 480gr or 500gr ever been thought of as lacking penetration, especially with modern softs and solids?
If I were buying new, I'm not sure that Norma .500/.416 load with a 450gr at 2150fps makes enough difference to warrant a .500 sized rifle over a .450 sized rifle, assuming a maker that uses different scaled action sizes.
Personally, I think that the .500/.416 should have been a .450/.416 3" (or even 2 3/4"), but that is just me