My experience with RL17 in the WSM puts it on par with the WM in most cases. I.e., a few years ago at the local shooting I was shooting 180 E-Tips through my 24" WSM over a chrony. The guy next to me was shooting 180 somethings over a load of RL22 through his WM. He asked me to shoot a couple of his rounds over my chrony. They were going the exact same velocity as mine, which was about 3200 fps. I also got 2935 fps shooting 210 Bergers.
That said, not everyone gets 3200 fps with RL17 and 180's in a WSM, but most get 3100-3200 which is still basically equivilent to the WM most of the time. I would imagine RL17 would give good results in the WM as well.
With the standard powders, the WM is going to be about 100 fps faster than the WSM, give or take.
If you are going to a build, use a long action for the WSM if you choose it. The short action will require you to seat bullets down into the case if you load to fit the mag box which will cause a loss of efficiency. I loaded mine to just off the lands which gave me good case capacity. I loaded one round down with nose of bullet just above the box for a second shot repeater.
Both are capable to 700 yds plus.
Welcome to the forum and good shooting!