Some info from Accurate shooter. http://www.6mmbr.com/7mm284.html
They seem to prefer the 7SAUM and the velocity difference between it and the WSM is only 30 fps with their loads. I favor cartridges that have Lapua available as an option.
Another one to consider is the plain .284 gets better barrel life than the 6.5 version. But any of the cartridges mentioned would be good.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli