Re: what about a 6mm wsm
That is a lot of powder behind a little bullet. A couple cons would be barrel wear, and to get the most out of it you would need a long barrel. If a close shot presents itself then most bullets will not stay together good enough and even a decent shot placement may not end up being lethal. I shot an antelope once with a ballistic tip impacting at about 3800fps. Witnesses saw the impact and it looked good. The antelope instantly dropped, but then got back up and ran for as far as we could watch him(about 2 miles). The blood trail didn't last for 50 yards.
The pro, of course, would be really flat trajectory.
As you could probably guess... of the two you mentioned I would go with the 7 wsm. All around a really great performer on a wide range of game.
The main question is how far do you want to be able to shoot a deer. Something in the 6mm caliber probably would be a good option for you.
Hope this helps