So the WC international affiliated lounges seem to be the most extensive compared to CRC and PC so you have more access to international lounges.
Another thought is to get a Biz AMEX Plat $300 annual fee + $150 for the add'l card. It get you into each club when traveling the respective airline. HOwever, if flying say NW at IAH, you don't get access to the PC. With a regular membership you would have gotten in though.
I'd go with the WC membership
Don't forget the double miles for 60 days deal:
http://nwa.com/features/espr6/