With Tiger or Jetstar you will get A320 experience, making you attractive to the other A320 operator if your current employer lays people off. Easy switch over.
With Virgin you will get, hopefully B737 time but QF are difficult to get into and may only be looking for B744 S/Os.
Tiger are expanding and could offer quick promotion, Jetstar have A330s.
What does you crystal ball say regarding the long term prospects of the three airlines ?