I am going to build one or the other off of the Montana 1999 short action in a 24" #2 couture for my main sheep and goat rifle.
If you had the choice of either which would you choose and why.

The 6.5 WSM has a little more case capacity, so theoretically at least it should give you a little more velocity (all other things being equal). Brass for the 6.5 Rem Mag is no longer made (nor ammo), so that should be factored into the equation. I guess for conveniance I would go with the WSM based cartridge, but I have to say, I always liked the 6.5 RM. - Dan

Hey 35nut,
We oughtta talk, neighbor. I'm building a 35 WSM on the Montana Rifleman short action, and a good friend is building a 338 WSM. MPI makes a nice Featherweight stock for the M70 that should fit. Email me your phone number at jwatkins@customcpu.com.
Jerry/AK

I agree that the WSM case will give you a little more velocity than the 6.5 Rem. On the other hand, the 6.5 Rem will give you one more cartridge in magazine capacity than the WSM. You pay your money and you take your choice.

As far as brass availability, the 6.5 Rem can be made from virtually any belted magnum case with little trouble. If you can't find dies, just get a set of .264 Winchester's and saw the bottom 1/2 inch off -- that's what I did and it worked fine.