I agree with you. I don't even hunt whitetails with anything smaller than 250 grainers in my .348 WIN.

I think with 500 gr and heavier, .45 caliber and up, well constructed bullets, at ranges at which large and dangerous game is typically hunted, velocity and even sectional density decline somewhat in importance. Solids of this sheer mass at reasonable speeds (yes, room for debate here, maybe 1900 fps plus) penetrate well (even on thick-skinned game), make large enough wound channels, and do a lot of tissue damage. 12 bore 500 gr round balls at slower velocities than that took a lot of big game in the early muzzleloading days of African hunting, and 500 and 535 gr fifty caliber bullets with SDs south of .3 have always penetrated well at moderate terminal speeds.

I think higher energy levels transmitted to the target do result in more shock and stopping power, and velocity can and does play a role here, but within reason I would never trade off caliber or bullet mass. Hence my preference for facing a grizzly with a Trapdoor .45-70 versus a .220 Swift, and for that matter a cape buffalo with a .470 NE versus a .375 Wby.

Just my $.02.