That's a pretty typical notion: A cartridge that kicks harder will kill quicker.

I've killed 6-point bulls with .300 Winchester and .300 Weatherby Magnums. They worked fine, but the 6-point that went the least distance before falling was shot with a .30-06.
That's with typical heart/lung shots. Did shoot a 6x7 with a .300 WSM and he went right down--from a spine shot at the top of the shoulders. So the .300 WSM must be elk magic!

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck