I'm with Saeed that a 300WM is a much bigger gun than it used to be due to advancements in bullet construction. If all else is equal you and the game animal struck won't feel a damn bit of difference between the two on both ends. The 338's advantage is length of barrel life. I burned out 3 300 barrels to 1 338, that's when I turned my back on the 300. Then I switched to a 338/06 and never looked back.

So the short answer… Barrel life.

OK for now...we'll take it up again in 2020 :-)