Note that on many Virgin Blue aircraft, the seat pitch is not the same throughout the aircraft. So its no possible to make a blanket statement about Virgin Blue having more seat pitch than Qantas. It all depends on which seats are being compared.
It is common that the Virgin Blue seats towards the front of the 737 aircraft have greater pitch than the regular Qantas 737 economy seats. This is partly due to the fact that the exit rows have to be at a fixed position in the aircraft (aligned with the emergency exit door/windows), and evenly spacing the rows forward of the exit row gives a slightly bigger pitch than the rows evenly spacing the rows behind the exit rows.
Qantas regular economy rows seem to be more consistent in pitch throughout the aircraft, as they can adjust the variation in the business class seats.
So score a seat in the front half of a Virgin Blue 737 and you will likely have more leg room than a seat behind the exit rows or an economy seat on a Qantas 737 (with the obvious exception of exit rows, row 4 on a QF 73H and the convertible seats on QF 734s.