For what it's worth I used to have top tier status with US prior to the merger with AA and I target all of my earning to BA. That said, AA non-saver availability has been very poor lately, and that's the only availability that is made available for avios redemptions on AA. For times like this, if I really need a redemption booking, I still have a fair pile of AA miles, but mostly I just accrue enough on AA from some level of credit card spend rather than crediting any flying to AA. That said it's often a better deal to accrue points with Amex which can be used as cash bookings rather than reward bookings, and are often a better value except for last minute bookings when prices are higher and thus require a higher number of Amex points.