Probably need a uni graduate to give the best insight, but if you're eligible for HECS, then use it. Wouldn't recommend a third party loan.
If your parents are willing to pay your uni fees, then I guess you could consider that? Really it's quite unrealistic to expect to be able to pay the several thousand dollars per semester over the duration of your degree by yourself (without placing significant financial strain on you), or even expect your parents to do it (unless they're willing, of course).
It means you get to delay the payments for your course until you earn over the threshold, so basically until you have a full-time job.
It's essentially interest free (iirc), but is indexed against the CPI so that it maintains its "real value" - so you pay a sort of interest that isn't technically interest. You pay back your HECS debt at a determined rate depending on your income - people who earn more, pay off a higher percentage of their debt. I'm not 100% certain, but I believe your compulsory repayments are deducted from your pre-tax pay, so you don't even have to make conscious payments to the ATO - it's done for you (someone please correct me if I'm wrong) And you can also make voluntary payments so that your debt is paid off sooner.
Probably worth having a read of this website:
http://studyassist.gov.au/sites/studyassist/helppayingmyfees/hecs-help/pages/hecs-help-welcomeBut don't stress too much! Really, most people just HECS their degree and forget about it. It's a scheme that allows people to get a higher education degree when costs may be otherwise prohibitive, and is in my opinion, the best method to pay your uni fees unless you've got tonnes of cash at your disposal.