There are two angles covered quite nicely in the original post;
1. QANTAS is quite obviously trying to reduce the cost of its work force, fighting the unions is hard. Its easy to make some of your employees feel unloved and they leave until you have those that dont mind lower pay and conditions. This is easier to do than fight over agreements etc...
2. VA is expanding and offering opportunity but on lower conditions but higher freedom to operate or progress and a perceived higher respect for staff. (JQ is similar but on a lower scale again).
In the end what makes you happy is the most important thing to consider. Whether all these people make a difference in the long term is to be seen, VA is kicking all the goals at the moment if that is to be any guide.