Thanks for the responses!

As for FB and the reasons why I'm considering it -- US residents can get Flying Blue membership -- I already got that online -- and in fact there is an advantage to doing so -- you only need 40K miles for Gold if you live outside of France AND you get ST plus at the Gold level with the associated lounge benefits for just the 40K. I have a friend who has that on FB which is how I learned about it.

But I would lose the upgrades, that's true and that is a real advantage to CO as I get upgraded fairly often when I fly domestically. And I've had really good experiences on CO. The ony time I was treated badly ex post I received excellent compensation and apologies for that treatment from CO.

It is when I fly internationally that I wish I had FB as I would be Sky Team Plus or Worldperks because I would then be in World Club and have better lounge access. So I guess the deal in making this decision is whether international or domestic flights will predominate in the long term and I need to figure that out.