Although it is true that if you are a PC member you have access to the WC. It is not true though that you have acess to all the WC "affiliated" clubs. For instance NW is still affiliated with America West and WC members have access to their lounges, CO broke off from America West and PC members lost access to those lounges. Domestically there is not a lot of difference, some America West and Alaskan Air clubs WC members can access and PC members can not, however, I think the biggest difference is seen in Europe and Asia where the WC affiliated lounges seem to be more plentiful than PC affiliated lounges.

I made the switch from CO gold to NW this year. They just have a better program overall and I can still use CO metal when ever I choose (which is not very often!)