In my opinion having owned each of the 2 calibres you mentioned I dont think the Elk would notice a difference in what calibre killed it. Choose a premium bullet and make sure your rifle shoots it well and save your shoulder the extra 2 1/2 pounds.It may not sound like alot of extra weight but believe me when you have a packboard on loaded with elk quarters its gonna suck hauling around an 11 pound rifle!! Been there, done that, dont like it one bit!!!

Have a safe, successfull hunt!