For lounge it is clearly OZ. In fact once you get Diamond, it lasts 4 years.
So you can then look elsewhere for the other benefits
UA needs BIS miles for lifetime. 1MM= *A G for life. You need 50 r/t from PVg to LAX.
UA also has the advantage of Economy Plus - good for long flights.
LH has some good benefits esp op-ups.
Since you are based in Asia OZ may be good, or just stay with SQ.