There is a marked difference between the two.
11.2 on left / .416 on right

The 11.2 is a very powerful round but I think its demise had more to do with the bullets offered in it's day.
The .416 has a better sectional density and was offered by more makers than the 11.2.
That said, with a good bullet the 11.2 is capable of taking any game animal on earth.
As for the rebated rim, you can see it certainly is, but not any more than a .425 Westley.