Well, AA's new 772 is OK.

On BA you're guaranteed a flat bed, where as AA could change to an older aircraft if you're unlucky.

The BA seat is better for sleeping than the AA one for tall people (if that matters for you). BA sleeper service will be better for sleep also, compared to AA running a meal service for an hour and a half at the start of the flight.

Both aircraft are (relatively) noisy and dry so that doesn't matter. IFE is of similar quality on the BA super J and the AA 772.

I think you have to bear in mind that you have to change timezones sooner or later and taking the later AA flight will put you in London still firmly on US Central Time after a bad night sleep. Taking the earlier BA flight and trying to go to sleep early will start to shift you towards UK time during the flight.

I think it's a personal choice: if you are convinced you can't get to sleep on the earlier BA flight then take the AA one, if you would prefer the 747 UD and an earlier departure on a sleeper service then take BA.