The .41 Magnum was designed for people like me who want an excuse to buy another (or several) gun(s).
Having said, and done that, I recently sold off my two M57s, and my M657-4 3 inch; keeping the M58 (forever).
It was time to thin things out and a .44 Magnum/.44 Special (N-Frame or Ruger) will do anything a .41 Magnum will.
Elmer was probably the first to say the .41 Magnum shot flatter, his explanation by way of shooting it at longish ranges and noting its impact versus the .44 Magnum. Not in any way technical or scientific.
Soon after, as is often the case, many gun-writers and shooters just simply repeated Elmer.
And...shovelwrench is on to something. A safely loaded .45 Colt (Long Colt to get someone's goat) utilizing a 250 grain bullet at 1000 to 1100 FPS will kill anything as well. Not considering a Ty Rex.