I think a lot depends on what motivates players to make a move to the Antipodes. Others have commented on that already for example that for some it could be "resuscitating" their career stalled through injury (Hooper) or by lack of exposure (Davila).
But what I do not know is what motivates locals (AUS/NZ) to come home from Europe while still in their prime. So I am less interested in the reasons why McDonald might be back in HAL (first WU now Roar) as he is still a very good player but clearly in the later stages of his career. I am more interested why someone like Marco Rojas would choose to come back to HAL when he is still in his prime.
and that is something that is un-answered. This guy kills it in the a-league when he is close to home. Yet twice now he has returned from Europe - turning down contract offers to allow him to stay. WHY? does he get homesick?, does he not enjoy the European winters? Is the training too hard? or expectations too high? Only Marco really knows.
Out of curiosity is he married? Or long term partner? Otherwise do his Kiwi-Chilean parents live with him wherever he goes?
Having a close stable relationship with someone, just generally leads to more stability full stop.
I see his Danish side SønderjyskE were based in Haderslev (3 hour drive to Copenhagen, 2.5 hours Hamburg), a small Sth Danish city of 22,000 inhabitants. That's just bigger than my old home town Masterton. Maybe he just got a bit bored/lonely under 6 mths of grey Danish skies. Happier back in a happening Melbourne of 4M folks, mates around, and plenty of summer sun.