Recently having searced and booked and Aust-europe itinerary, I can echo that BA is more accurate.

Although I actually came across a situation in erverse - I had found a CX flight on Asia miles and a connection on AY. When I called AA to book, the CSR was happy to book it for me but then said what about an earlier flight that day which made it a better connection!! I said sure - that flight did not show availability on Asiamiles