As someone who uses both, KL/AF tech is way ahead of BA. The KL app offers luggage tracking, rebooking and everything is native, no dropping out into the website. And it has worked, consistently, for me without generating spurious new exec club numbers, deleting my miles balance, all of my bookings, refusing to OLCI and require regular logging out/back in again and all the other faults that the BA app has chucked at me in the last 3 months.

Objectively BA's tech is dire and doubly dire for an alleged top tier airline.