I find that the first main meal is generally better on BA, but AA wins out on the second meal/snack and this is most noticeable on the westbound. AA will give you a hot pastry snack and a muffin and soft drink, whereas BA will give you a mini sized chocolate bar and a drink (though I think they might have been improved slightly now?). It all depends on how important food and drink is to you. Personally, I would also consider the plane type in my decision making if there is not much difference in price and timings (eg. refurbished vs old 747s, twin aisle vs single aisle etc)