You raise some interesting points - I am looking at the other side of this now as I am now US based and a GGL - so will be flying BA alot less now.

So far the uses have been being able to pick any seat on AA (and MCE seats if I am in Y) and the use of the lounges (but they are pretty basic on the whole here apart from LAX here on the West Coast).

BUT - I can't get near any of the complimentary upgrade lists even on flights where there is availability.

I'm going to stick with BA though for a bit longer as I am close to Lifetime Gold and want to have that as a backup before switching. But will lose my jokers sadly - which are a big deal with a family.