I've done a significant amount of travel recently across the pond (AA & BA) and domestically with AA.
If you are flying in Y and have access to AA's new 77W as well as have either Emerald or Sapphire status, you could be made not to travel on AA. A new aircraft, combined with significantly better legroom means that AA's new MCE product as fantastic. Food on AA tends to be better than BA, and as an Emerald, you get free booze. I cannot speak about booze in respect to Sapphires.
Service on AA can be hit of miss in any cabin, but in my recent travels I have found the staff to be very good leaving the US, and fairly bad leaving the UK. I will let you all decide on why that may be. I've done enough flights lately to see this is the case on every TATL sector and appears to be the case in either Y or J.
If your budget extends to WTP, you would be mad not to fly BA.
In J, things get a little more complicated, but again if you are able to get the new AA 77W product, as a general rule of thumb, AA is better. The new 772 seats will be very interesting to try too, but it is still early days and we really won't know much more till September. I'm not a fan of the Thompson Vantage seat, so the new 767 seats won't be my choice unless I absolutely have to fly them.
In summary:
- If in Y and have mid-tier status and above, fly AA which gives MCE (OWE/OWS) and free booze (OWE)
- If in W, fly BA
- If in J, depending on the aircraft type and seat configuration BA or AA maybe appropriate, however my list goes like this (assuming the new AA 772 is as good as it looks): AA New 772 > AA 77W > BA 747 > BA 77W > BA 777 > BA A380 > AA New 767 > AA Old 772 > AA 757 > BA 767 > AA Old 767.
I won't call out F as I have not tried the new AA F product. I do love the comfort of their old seat, but it is pretty tatty these days.
In general I prefer AA food to BA, but prefer BA booze in any cabin to anything served on a USA based carrier. Service also tends to be better on BA, but not significantly so. The new AA product has definitely put crew operating the flights in a better mood so it is getting harder to call it. It will depend on their mood as well as yours!
Domestic USA despite being dreadful is still better than the even more horrendous product we all have to put up with here in Europe, whether flying J or Y. Recent cuts by all European carriers mean that we (Europe) are bottom of the pile despite any of the usual protestations to the contrary you read here. Carriers from both continents could learn a thing or two from Asian and Australian carriers, but I digress.....
I can't speak much for US, but my SO likes the new US 332/333 seat which was actually the first carrier globally to feature the much loved Cirrus seat. I also believe US's 767s are very much on the way out.