Either one would be right for the job you have described.

I don't have a .300 magnum of any stripe, but I do have several standard thirty calibers and I would use any of those on the game you list (with appropriate premium bullets--minimum weight of 180 grains--and at appropriate maximum ranges--200-250 yards). So, IMHO, a .300 WSM, with its greater power and range, would therefore be even better.

But I also have a .338 Win. Mag. and it is my favorite African plains game rifle. I have great confidence in this caliber out to 300 yards, which is my self-imposed limit. It hits very hard and just flat out puts 'em down on the ground fast!