Quick comparison of BA and AA JFK-LHR. BA was in Feb 2022, AA was last week.

Seats are pretty much identical, I'd struggle to notice a difference. Food was probably a tad better on AA when it comes to dinner. Main difference is in the breakfast. BA was a croissant in an enjoy your menu bag. AA was a fruit plate, yoghurt and warm roll on a half tray with proper cutlery. Bar service on AA was identical to economy. Don't remember if BA offered anything special.