BA's not giving AA miles (or redeeming them)
on trans-Atlantic flights is the main reason
I avoided AAdvantage in looking for a new program when DL trashed SkyMiles. They also don't give miles on BA for some fare classes.
Indeed, just about all of their European partners have the latter problem. Truth in advertising should compell AA to describe its European partners as merely ''limited partners'' and BA as a ''VERY limited partner''!