Are you trying to say you are an international student? If you are, you have to pay upfront and there is no hecs. If you are a citizen/PR, you can't get into a full-fee paying place (since 2009). You pay off your hecs debt for both degrees when you start working
USYD provides transfer flexibility, you can transfer even in 2nd/3rd year. With UNSW I think you can only transfer only after 1st year. It's not strange but it will be difficult and stressful in making new friends again. Just stick with UNSW.