I was about to cast dispersions on the .450/400 (400 at 2100) as being anemic compared to say a .470 or .500 NE, but clearly a 400 at 2400 from a modern rifle is another matter entirely. While I'm not a Boddington fan, neither do I entirely dismiss his opinions, and he is/was of the opinion, that for buffalo sized game, the .450/400 is a wonderful cartridge and should be more popular than the elephant cartridges. Maybe so, but the thought of a .50/580 at 2150 still gives me a warm fuzzy feeling when I think back to that day we managed to get in amongst a herd in the grass.
In terms of a .416, I was totally impressed by the power, trajectory, and versatility of the .416 Rigby in my #1 (a 350 gr X or Magtip over 102 grs of H-4350 for 2850). As a result I was never taken with the Remington version which I still believe could have been so much more had it been brought out on the Ultramag case. Still, the .416 Remington has performed well on the world stage, equalling if not surpassing the original Rigby performance, and it seems reasonable to expect the .450/400 in a modern rifle like the #1 to match that level of performance.