Guess it depends on whether you’re flying BA (LHR-HKG, LHR-SIN) or CX (LHR-HKG-SIN or other Asia City) mainly. If latter I understand (anecdotally) from my MPC Diamond colleagues that they get upgraded rather frequently, as CX takes care of their Diamond members well. If you’re flying mainly BA, then sticking with BAEC is quicker to rack up status from flying PE.