While I've never owned one, the 338WM from what I've read is a great cartridge for everything this side of the Atlantic and for most game on the other side too. But I have owned a 300 WM and still own a '06. IMO there isn't nothing the '06 can't handle in NA using the proper bullets. The others will also do the same but with more recoil and more ammunition cost. Yes you can load the bigger two to '06 ballistics. So if you're going to do that for the majority of your shooting why not just get a '06? The two moose my friend an I shot with our '06s this past October couldn't have dropped any quicker if they were hit with a 458WM. Its all about bullet structure and placement.