Better wine, food, seating options, and service (and usually fewer other guests) in the BA F lounge are the reasons why this is my choice. I haven't had a spa treatment there- I can't recall if you need to be on a BA longhaul flight to qualify for spa access.
CX is good if you want some noodles or dim sum.
Hit the AA lounge on your way to the gate to check if the boarding is still on schedule (the BA lounge can't help you with that.)