I've only done CA J & Y on this route so can't compare. But I do know the vast majority of UK Tour Op's running big groups into China predominantly use CA as their Tour Op rates are far cheaper than BA, J upgrades reasonable - and allocations easier to source.
Won't comment on the flight as I got suckered into an old J 747 outbound, but newer A330 on the way back - no seat back entertainment on either - but I know CA have improved on this - it was a few years ago!