I have very limited knowledge of this but, about 3 months ago, was at a (public) presentation by senior service personnel. Shortages in the services were discussed, and Navy was said to have larger shortages in more areas than RAAF and Army.
Is it a case of 'better staff management'(?) in the RAAF resulting in lower retention bonuses?
I would say it's a lifestyle issue. In the RAAF and Army you spend a lot more time at home. In the RAN you can be posted to a ship for 2-3 years and spend 6 months at a time at sea. Cash bonuses wont work IMHO. In the current climate tradies can leave, make more money and enjoy a much happier family life. All without having to spend 6 months at sea putting up with military crap.
Same goes for pilots at the moment. There are so many oportunities in the real world that the ADF (RAN/Army particularly) are desparately short (hence Navy's Retention and motivation initiative A109Es).
Yes, the RAAF probably manage their pers better than the other two (definately better than the Army).