Not enough difference to argue over. If you are buying one or the other, I would would go with the 270 wcf for no other reason than ammo availability.

My brother has a 270 wcf, and his friend has a 270 WSM in the identical gun (Ruger M77 MkII stainless/synthetic). They sight in together every year and swear the 270 WSM recoils 50% more than the 270 wcf. This is based on their perception of the recoil and has absolutely no scientific basis.