AF:
Pro: excellent award availability, great 2 for 1 or redem C for the price of Y promos.
Cons: lousy partners, erratic ground service.
Qualiflyer:
Pro: Miles and any fare code including most OW carriers, upgrade on any fare on CX, good award availability, 24/7 call center in your language
Con: Major airlines are filing under cxhapter 11 (SR, SN)
BA:
Pro: Service, OW lounges (The Wing in HKG), the BA forum on FT, award redemption based on distance.
Cons: Maybe the most complicated program around (mileage accrual in Y only possible in certain fare classes, each of them different depending on the carrier/country you live in etc...), very few promos, no recognition from other OW carriers.