If you're planning on studying Commerce and prioritise employment prospects, then Commerce at UniMelb should be your #1 preference.
For context, I passed on a $8,000 per year scholarship from Monash and it was the best decision i've ever made. The monetary difference is easily made up within 2-3 years of working.
The development and personal growth opportunities at Melbourne are unparalleled and the truth is many top employers in the business field do care about what university you go to. It is definitely not the be-all and end-all, but there are companies that simply don't really look at Swinburne (places like Google, McKinsey and Goldman Sachs have never taken a single Swinburne graduate in at least the last 3 years). If you want relative security, going to Melbourne definitely does not guarantee you a job, you will need to work hard and truth is I'd guess that at least 20% of graduates are unemployed from Melbourne (perhaps higher at other universities).
If you want to work overseas, the company that you enter out of graduation has more of an impact than the university you attend. Most companies in America don't know the difference between UniMelb/Swinburne but if you join somewhere like McKinsey or Facebook straight out of undergrad most companies overseas will take you, or you could just transfer offices if that's what you wanted.
Also as a caveat, this only applies to studying Commerce. I don't understand enough about other degrees from UniMelb/other universities.