First off, what are you going to be hunting? Secondly, and I am not pointing fingers at you, but I've seen BIG men wince and flinch shooting even 30-06 chambered rifles. Rememer, the bigger you are the more resistance your body has to the recoil and the more it will absorb. Also, rifle designs, even rifles of the same make, model and chambering can have noticibly different recoil.
I would say that if you are definately leaning toward the WSM cartridges and you are not going to hunt anything larger than deer or black bear the .270 WSM will suffice. However if you plan on hunting bigger stuff I would lean toward the 7mm WSM or 300 WSM with the 300 being the most versitle. At least that is my opinion for what its worth.