Originally Posted by number_6
BA J has a flat bed which is great if you are 5' 10" or shorter, less great if you are taller than that (the bed is short and skinny, but flat and horizontal). AY has better food and wine, a very comfortable seat but not a bed (so snoozing rather than sleeping). So tall, hungry and/or thirsty people should fly AY, sleepy ones should be on BA.
Thanks for the tips. I'm tall (6'1"), but skinny (I do curl a bit when sleeping, although I'm guessing there's not enough width for that to matter much). The wife is 5'2" so she would love the lie-flat. However, since this will be our first transcontinental J flight, we may be too excited to want to sleep that much anyway (and we'll be staying with a friend in Beijing so we'll be able to recover nicely at his place). We also don't drink, so we won't appreciate any wine differences.
Via LHR does earn us 3500 more miles, 1550 of which are AA EQM which may be important to maintaining status. But this would be our only longhaul AY opportunity (the rest will be BA, CX, QF, and AA). So it sounds like this will be a tough decision to make (although I will calculate EQMs carefully and if those 1550 are needed, it's of course a no-brainer).