The .300 WSM outperforms the .300 Winchester Magnum....in the manufacturers' advertisements. The ballistic comparison shown in the new advertisements purposely show the .300 WSM in its best light (that' s why they call it advertisement) while at the same time NOT doing the same for the older .300 Winchester Magnum. Because the .300 WSM is a new cartridge it is currently " loaded to the gills" .....no need to worry about older rifles and rechamberings yet....and the .300 Winchester Magnum can be bettered by nearly any handloader.

One of the things the new short magnums will never do as well as the older standard magnums is launch the " heavy for caliber" bullets that make the big magnums such good killers, (ie. 200 - 250 grains in .30 caliber).

Having said all of that, with the 180 grain and lighter bullets, the new short magnums are very efficient. (But then again so is the .308 Winchester more efficient than the .30-06. But it doesn' t make the .308 Winchester better in all applications.)

If your use is to be on lighter medium game the .300 WSM will do all you need. If you think you are likely to want to use your .300 on truly heavy game.....the standard magnums are the way to go!

Good luck!

P.S. If you just want to own both, and can afford it, by all means have them both! After all hunting and shooting are about personal enjoyment.