I did the tables for Maths. Here they are:HSC Mark I believe is the raw exam mark and whatever the UAC has BEFORE scaling.
And for whoever asked me about the percentiles... I got it wrong (somehow), so I'll re-edit it to:
A P25 in Mathematics whoops P50 in General. So you might as well keep Maths.
http://www.uac.edu.au/documents/atar/2009_table_A3.pdf
Gen. Maths
99 --> 90.6 scaled
94 --> 81.4 scaled
86 --> 69.6 scaled
79 --> 58.0 scaled
71 --> 41.8 scaled
62 --> 26.4 scaled
Advanced Maths
100 --> 100.0 scaled
97 --> 94.0 scaled
92 --> 84.4 scaled
86 --> 75.4 scaled
77 --> 62.8 scaled
68 --> 48.4 scaled
A P25 in Advanced is :48.4, a P50 in General is 41.8. Not exactly whooping, but is a significant increase.
I'd imagine the extra time you spend to get those 6.6 extra points in Advanced would be taken away from another subject.