I have hunted elk in a lot of different places and sometimes wished for more magnification, sometimes less. An elk is a very large target that is handled well with a 9x or 10x out to 300 yards or more if he is in an open park but you need a much lower power setting if you are in timber or all you will see in the scope will be hair.
If you will be hunting sage flats go for more magnification, otherwise less is probably the best choice.