First off, residents are taxed on their worldwide income and nonresidents are taxed only on their Australian-sourced income.
Plus nonresidents tend to be taxed at a higher rate. In fact, starting 1 July 2012 all nonresidents making less than $80,000 will be taxed at 32.5%. Those making more than that will be taxed at 37% for income between $80,001 and $180,000 and at 45% for income over $180,001.
Residents, on the other hand, are taxed at a much lower rate. For the 2012-2013 financial year, residents will pay nothing on income from 0-$18,200, 19% from $18,201-$37,000, 32.5% from $37,001-$80,000, 37% from $80,001-$180,000, and 45% over $180,001.
One of the perks to being a nonresident however is that they do not have to pay the 1.5% Medicare levy that residents do.