I have both and Iprefer the .300 Win mag.They are both close in performance with theedge going to the .300 Win mag especiallyif you reload (likebigcountry stated) but I think itjust feels better toshoot. All things being the same (cartridgewise) it has a totallydifferent recoilthan the.300WSM. It'smost likely due tothe tworifles but it's way different none the less.The 300 Win magwhile having a heavy kick feels more progressive while the .300WSM feels more short and stout....hard to explain in words....
300 WSM is like a 7rem mag in the kick department even in lightweight rifles ..I wouldn't dream of owning a 300 win mag in any gun under 7 lbs. I have never ever had a 300 win mag shoot as well as any of my 300 wsm's never ever. They are one of the least temperamental cartridges out there.