<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by 70Jaguar:
Re metal selection, some other points are:
-NW upgrades the domestic portion of international trips, but CO does not.</font>
Can you clarify what you mean here? CO does give EUA's on the domestic segments of an international itinerary.
Also, one key thing to keep in mind is partners. There are some partners unique to each. For example, CO has partners such as Virgin and Qantas, NW does not. NW has partners JAL and Cebu Pacific, CO does not.
There are also nuances as to which count towards Elite and which don't.