I can't help too much with the Engineering, because I only did it for 1 semester before I dropped it.
As for the Maths there, it's actually quite good! My favourite part of it is the Special Studies Program (SSP) that lets you do 2nd Year or extra topics during your First Year.
However, I don't really like the fact that they don't record any lectures, and some subjects (Integral and Differential Calculus) don't have posted lecture notes. I don't know what it's like at UNSW.
Out of 10, I would rate the Mathematics programs 8.
-1 for no recorded lectures (though, a good textbook will suffice)
-1 for having some subjects with no lecture notes