I like them both. VS tries to be very cool, very chic. BA tries to be more formal, more understated.

BA has a front and back facing seating arrangement, as opposed to VS's herringbone, so if you've never flown backwards, now is the time to try. There are privacy screens so if you are travelling alone, you don't have to spend the trip staring at a stranger. Personal opinions vary as to which is better for sleeping in - I find i sleep in both. BA marginally better for lounging in, as it just reclines and reclines and reclines until it is flat. Better at seat storage on BA - I found VS a bit restricted for cubbyholes to put books and ipods etc in.

BA's IFE is better than VS. Food used to be better, but is declining on BA and improving on VS.

On the ground, VS has a much better lounge in the Clubhouse at LHR, but T5 is a nice terminal now as well, and the Galleries is well above average for a lounge - it too offers treatments, but sadly, no spa pool! Can't speak for the ground at NY.

For £500, I'd fly BA and take my own chance to compare the two.