There are three levels of Membership Rewards:
Membership Rewards
First (Centurion, Platinum)
Membership Rewards (Gold, Green, Everyday Preferred, Everyday Free)
Membership Rewards
Express (Blue and various discontinued cards, plus some free business cards.)
There is no longer any important distinction between
First and standard Membership Rewards, but
Express points cannot be transferred. The magic of the Everyday card is that it is free -and- participates in the full version of Membership Rewards.
Discussion here:
http://www.flyertalk.com/forum/ameri...day-cards.html