First I would choose based on total travel time, & price.
If that doesn't give you a decision, I would CZ if I have Skyteam Elite Plus. Lounges make transit better. If I need EQM to get Elite Plus in the near future, and am likely to fly on Skyteam carriers in the future, I would go for CZ.
If EQM are not important, I would go with MH. Assuming you are on the B772 operated flight, has got the best hard product among all choices. 34" pitch & PTV. The second sector on MH B738 might have PTV and the pitch isn't too good, but bearable. 9W also gets you PTVs, but I think their service is poorer than MH. CX will have PTV, but it will be likely to be the old regional planes, in which case you are better off reading a book. PR has no PTVs on flights from SIN/HKG.