Both are good airlines, I know people find differences between them, but it's for the birds in my view, both airline should give you a good experience. The only other factor not so far mentioned - and that may work better for CX - is the change fee. I know you don't book tickets expecting to change them, and I rarely need to do it, but stuff does happen!

Otherwise if there is a lot of baggage BA has a clear advantage, CX is pretty mean in comparison, and the hand luggage on BA is not 10 kgs, it's 2 bags essentially, 1 a full carrier bag, the other a smaller bagpack or something, which won't be weighed - you just need to able to lift them into the locker unaided.

Apart from the baggage issue, personally I'd go on timetable, and if that is no difference then go on cost, particularly if the BA service is the A380. 777 isn't brilliant on either airline, mainly thanks to the fact that 777s are noisy bone rattlers compared to A380s.