DANM
I think you'll find you were either in J class with a 2-3-2 config on a 777 or you were on a 767 seeing how you say the legroom was only 31".
But AA now have "more room through coach" so you'll find the seat pitch goes up to (about) 34" in economy.
To answer the original question - if you want space at a not too hideous fare (in econ) then I'd go AA. If it's frills & great staff I'd go BA. If you can afford it then VS Premium Economy.
cheers
FF