Ok currently sitting in CX F lounge in T3, having started in BA F lounge.
BA lounge had Kosher food available so that was a plus for us. Sat down and ate a hot meal on China plates. For those used to KSML anywhere, this is isnt to be taken for granted!
The BA GF was nice and calm and quiet - not always the case in T5 lounges which I am more used to. As noted by many, a great drinks selection. I'm a whisky lover and there was JW Blue, a good Glenlivet and Gentleman Jack. However, the chairs and decor were definitely tired and some areas were a bit grubby.
CX F lounge - definitely cleaner, calmer and more serene. Nice piped music. Drinks selection clearly more limited but I'm currently sipping a CX Betsy beer which is quite pleasant!
As I have said I can't compare the dining options but both have been a nice way to while away a couple of hours, away from the nasty hustle of the main T3 terminal