Another potentially big difference is Avis status. The old CO card continues to give Avis President's Club (which is almost impossible to obtain otherwise, and can be a Big Deal if you rent cars a lot), whereas that benefit is going away from the new Club card. Frankly, this is a lot more meaningful to me than the 1.5x miles (I have other cards that get me 2x miles on most of my purchases).
This is probably the one perk that I do feel truly "elite" with. Hopefully that doesn't change.