BA lounge is by far the best one, AA FL is very dated and crowded, with poor quality food and drinks, while CX F section used to be good but food quality is now poor (mostly sandwiches from the BA J lounge ). Though CX F can be very quiet at times. The allure of using CX lounges in T3 was when BA had shut down its lounge there (prior to the move from T4), those days are long past but live on in google searches