At least AIPA provide better support should any incident occur oversea's (which JQ seem to be doing more of these days). It cost's less to be a member of AIPA compared to the alternative, and at least AIPA have said they will channel a percentage of the membership fee to the JPA day to day running costs.
Anyway, as a side note, just look at how the QF Engineers all stuck together recently. Its amazing what happens when everyone is singing to the same song.