They earn same as CX I believe. Another advantage is if you are booking with CX and fly PE they book your dragon flight in an economy flex bucket. This meant that when I did LAX to Bangalore via Hong Kong, I got 340 tier points in PE and economy. 100 each way for the PE in CX and 70 for the economy legs of Hong Kong to Bangalore. If I'd gone economy would have been a lowly 60 or something. There again, even more on offer if you go business.