RE: 270 win VS. 270 WSM
I load for both the 270 and the 270 WSM. Its no problem loading for the WSM the loads are no more apt to be compressed that with the 270 Win. That part depends on which powders you choose. In most cases you will find that across the chronograph, there is only about 200 fps Max difference. The most accurate load in My WSM is the 130 grain Sierra Pro-Hunter which clocks at 3050 fps. I can get more velocity but then the accuracy drops off. I have not tried very many combinations in it so far. The WW Supreme 130 Grain Ballistic Silvertips closk at 3275 from the WSM. The 150 Grain WW Power Points clock at 3200 fps.
My choice would be the Remington SPS which comes in both calibers and the 270 Win has a 24 inch barrel. I honestly don't think that in the field, you would see much real difference in performance between the two. The 270 WSM would give you a little more velocity, the Winchester version would give you less recoil and just a very little less performance. Last fall I took nine mule deer with nine shots with the 270 useing 130 grain Federal Fusions with very little meat damage.