Between two great universities like USYD vs UNSW, I would say follow the money if you are generally like Sophie's Choice can't split the two.
That said, you should never sell out for money if you really want to go to UNSW more, but considering it's the same course at both top unis I'm not sure if the choice will be as divisive for you. But if you truly really want to study at UNSW and don't at USYD, don't let the money sway you. You can always earn money, but it is a big help at university.
If you look up any number of uni rankings, both have good rankings in engineering and for example:
http://www.topuniversities.com/univ...ankings/2013/engineering-civil-and-structural
See this for civil (take with a grain of salt only one ranking system), USYD in civil is 12th and UNSW is 15th.
Check for any subtle differences in subject/elective freedom, major options etc. between the two institutes, I'm not conversant with any differences in university.