More important is your ticket and the metal must match. I was not admitted to a NW club when I had a NW Ticket but it was KLM metal. I has a similar experience at a CO Club.

I have been using the AMEX Platinum because of some other advantages like the Emergency Medical Evacuation. For normal charge purposes I use the Starwood American Express.

I have thought about getting a Priority Club Card, but it seems like their rates have gone up although there have been some specials I have been offered in the mail.

I also use a Diners Club card which helps me in many overseas locations.

I like the suggestion of the NW two month trial. Since I have lots of NW trips overseas in the next two months, I may try that.