Well lets see if I can respond in a semi-intelligent manner. There are two ways to look at this. From the North American hunting perspective, the Rigby and Weatherby rounds produce the same trajectory that many riflemen are used to, so a longish shot is able to be made intuitvely with those rounds. The Remington probably isn't that far behind, but if 8" of drop was allowed at 300 yards, it might hit low. With respect to recoil, I doubt that anyone who is proficient with a .416 Remington would find a hot loaded Rigby unmanageable. I loaded mine with 350 gr X's to 28 and change, and could hold for 3 rounds prone, and I'm no tougher than anyone else.
From the African point of veiw, the Rigby/Weatherby capacity cases provide enough volume to prevent a heat induced increase in pressure that could result in sticky extraction. The Remington is loaded to maximum pressure just to get the 400 gr slug going 2400, and that would in all likelyhood have to be reduced to 2200 to beat the heat.
To me the .416 Rigby/.416 Weatherby represents the biggest cartridge that shoots flat enough with low enough recoil to be considered a general purpose hunting cartridge. A .460 Weatherby might very well have a similar trajectory, but would be all but unmanageable from prone. The .416 Remington, and I believe the same applies to the .416 Ruger, produces the magical ballistics of the original Rigby load when used in temperate conditions, but in the heat I don't believe its as good a choice. This is a situation that will be exacerbated if one chooses long, heavy for caliber bullets, or even mono-metal bullets that seat deep down into the powder capacity of the case.
A .416 Ultra would split the difference and be cheaper to load than the big cases. It's been 10 years since I had my Rigby, and even then 50 empty Norma cases cost $180, I'm not sure what they cost now. I have almost 500 peices of Ultra brass, that would have been the cost of a new rifle had it been Rigby or Weatherby brass.