EdK, somewhat along these lines, the 454 is said to be more "sharp" in the recoil department. In the theme of the same weight bullet in either cartridge, I did shoot some 385 grainers in my 475, much lighter than my normal 440's, and th recoil was noticeably sharper, actually much less pleasant than the heavies. If this helps prove your theory, it may explain the difference in perceived recoil. Given the same weight bullet, I bet you are right, they probably kick the same.