In my opinion there is no longer a debate on this. AA product wipes the floor with BA who in comparison are light years behind. Hard product is vastly superior, food in my experience is significantly better. It is plain simple food served well. Wine is a weakness as are lounges but I spend an hour in a lounge and 8 in the plane.
Crew are fine but can be a little rough round the edges but again my overall experience has been positive.
If you use codeshare you will get tier points and avoid and flight counts as BA sector.
Rows 3 and 4 are the place to be but there is not a bad seat.
Finally, the 5pm. LHR JFK arrives in JFK at a quiet time and in April I was cleared by immigration and customs within 20 minutes of pulling onto stand.