Have a look at the "Which oneworld program to join" thread: http://www.flyertalk.com/forum/onewo...help-here.html. (where you should have posted in instead of opening this one - it'll probably get merged there)

Generally, key element in choice of programs is what you want from it. For shorthaul flights within Europe, BA is indeed a very good choice thanks to RFS. For longhaul premium cabin redemptions, especially taking surcharges into account, not so much.
As you say that you fly paid F on Qantas, there's not much you can gain by having status with them (see the recent What is Platinum One really worth? About 1 bottle of champagne... thread there). There is nothing to get upgraded into, and as an F passenger you are already getting treated well.

Gleaning from other threads on here, it appears that QFF is mainly interesting to Australians who can (and do) earn points through non-flying activity, but not the best choice as a FFP. You may earn more miles than you do with BAEC, but the redemption cost is also very high. A lot of frequent fliers have recently abandoned QFF for BAEC and AAdvantage after particularly nasty devaluations.

If your goal is to maximize earning for longhaul premium cabin award travel UK-HKG on CX, look at Marco Polo and Asia Miles. As a Diamond member, you'll get systemwide upgrades you can use for your family, and also have advance access to reduced mileage award inventory. It can get rather tricky getting a whole family on one flight on award tickets in a premium cabin these days, with airlines managing award inventory more granular than ever, so this is a nice benefit.

If you fly enough (that's to say way more than it takes to qualify for Emerald status in any one program), it is also an option to split earning between programs. In your case, credit to BA so you'll have enough Avios for those intra-European trips, and the rest to a program that will provide you with a better value for those HKG trips (AA or CX).
Although my primary program is AA and I credit most activity there, I always see that I have some Avios (for short intra-US domestic flights on AA which would cost a lot more using AA miles, or intra-EU RFS awards on BA) and airberlin topbonus miles (so I can take advantage of their "topdeal" redemptions which are a very good deal).