Perhaps the bigger issue is who has the better Premium Economy cabin as that's what you will be flying most of the time.
The Points Guy reviews Cathay's PE:
https://thepointsguy.com/reviews/cat...econ-777-a350/
And BA PE:
https://thepointsguy.com/reviews/ba-...8-789-and-747/
He strongly prefers Cathy as you will see after reviewing the articles.
All the best.