If it is a level playing field on ff miles and the airport for the flight is the one you want to have, I'd go for BA even in the cheap seats. BA has the slightly more expensive WT+. AA does not.

The food on BA is better.

If ff miles matter to you and you are already a BAEC member, then you need to do a lot of pencil work to make your decision. The best value in flying may be the use of BA miles to upgrade.

If you want a wad on ff miles, make sure your ticket on AA will give you those and choose AA.

So here's my list: airport choice
ff miles, type and quantity
price