Backpack or suitcase

This is a bit of an odd one.

I'm doing my WHV in Australia in August and I'm just so unsure whether to bring my Osprey 70L backpack or just bring my suitcase.

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I've done Australia before for 3 years and just had my backpack but I'm old now. Although I'm less about the party and stylish clothes I don't know if I can be bothered with the faff of a backpack again... But then again lugging a suitcase around could also be a pain...

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Does anyone have any pros or cons of either?