But ARN-LHR on BA in CE should be a new 'long-haul' CE concept (starter and main course served separately). In this case BA might actually be better...
I'm not usually starting from ARN, but I'm indifferent to band 3 BA catering wherever I'm coming from.
However, two reasons to avoid BA like the plague are the awful seat pitch (except in row 1) and uneven BoB offering down the back. It's SK (nearly) all the way for me these days.