Hey Ash. To be elegible to study under the mature age scheme you need to meet certain criteria, such as being over the age of 20 when your study starts, have no tertiary record AND no results in your HSC (or equivalent) that are capable of getting you into university. usually this is anything below ~60-70. So if you have a UAI of 70, unfortunately you are not eligible to study under the mature age scheme as you have the ability to get into university already.
Mature age schemes run by the UNSW and USYD are pretty equally regarded. One doesnt have more of a chance getting in with one Uni's pathway or the other. In fact, the entrance courses run by both universities are accredited at both uni's, so you can sit the mature age prep course at USYD and then apply to UNSW, or vice versa.
This is good because the prep courses differ somewhat between the two universities. I studied the UPC (university preparation course) at Sydney University. You basically need to study a set of subjects relevant to your course in interest. These are prerequesites to be accepted into your chosen degree, and are listed in the mature age handbook. So for example, to get into a bachelor of Exercise and Sport science, i needed to study the UPC science course and the UPC maths course. These two subjects are the norm for any science based degree usually. If you wanted to do something humanties based, you most likely will be studying say psychology or philosophy and something else.
The UNSW prep course is a little different. For my course, which is a science degree, you needed to sit what they called "the science stream". Oddly, this doesnt involve any science in it. All you do is sit a maths stubject, and a compulsory study skills subject along with it (how to write essays, seminars, do research, etc etc). You may think this will be easier pathway than sitting two full-on subjects (science and maths), or you may think this may underprepare you by not sitting a science course, its at your discretion.
Either way, they are pretty much equally regarded. Id probably choose the prep course at the university you want to actually study at. Although, as mentioned, this is not a requirement as both prep courses are recognised at both universities. There are ofcourse other methods of getting in mature age, such as the limited uai and the TPC, but they require alot more hours (they are pretty much full time). UPC is great in that its only a few hours per week - you can live your life, work etc while studying and having a second chance to get into uni.
if you want to know anything else, feel free to ask
