id go amex plat. if you dont really see a need for int'l PC memebersip benefits, then go with the plat. basically, plat gets you a domestic version of a club membership with NW, CO, DL and another. USAIR i think. as long as you're ticketed with the club's airline, its basilcally the same.

when traveling internationally, the plat doesnt give you access at CO's reciprocal lounges that would normally be afforded to PC members. however if you fly BC or FC internationally, skyteam gains you access.

keep in mind, also, that plat amex gives you a load of mostly useless benefits, but if you really dig in to and try to take advantage of, its benefits, the plat card actually comes with quite a few more perks than a normal PC membership.