Easier to get brass. Also read it was more effiecient & easier on throats according to the article on 6mmbr.
It's pretty easy to buy all the WW brass you want for the 7WSM.
If you prefer other brands of brass then yes there are more choices for 300WSM brass.
As to being easier on throats that would only be because it's slower than the 7WSM. There is no magic in the 300WSM case which is lost when the shoulder is pushed forward .038".
