Good advice Gordo.
You do indeed get the full complement of TPs when flying with oneworld partners.
The only disadvantage of flying Cathay over British Airways is that if you have a BA Gold or Silver Exec Club card, you will not get any bonus miles (which would be a not insignificant 50% and 25% bonus respectively), and of course cannot earn onbusiness points.
You still need the four minimum sectors on BA to maintain status, in case that is a consideration.
Cathay’s new Business Class seat :
has not been that well received, with many feeling it narrow and claustrophobic, though CX is generally felt to be superior if you were upgraded to First.
There should be some excellent premium cabin fare sales coming out in the next fortnight, so it might be an idea to keep your powder dry before rushing in to book.