"A difficult task postponed, becomes an impossible task later."
The graduate medicine entry route requires that you complete a degree first before applying for Medicine. This means studying hard for an additional 3 or 4 years (and paying the fees), to maintain high grades with no guarantee of getting into Medicine. So you will have exams for at least 7 years: three years of first degree and 4 years of condensed medical degree. Undergrad medicine, for eg at Monash, is far less stressful because in the first year they ease you in, and in final year you are working as an unpaid intern (so no exams).
You also need to sit a test called the GAMSAT, which is a six hour test (compare this with UCAT which is a two hour test) as well as doing well in the interview. The preparation courses for GAMSAT are also far more expensive, in the range of $1500 plus.
The GAMSAT has been described by most people as ‘the most horrible thing I've ever had to do in my life’. Do not make the mistake of thinking that if you do a Biomedicine or Biosciences degree, you will automatically be offered a place in Medicine, as some universities misleadingly make you believe. If you miss out on a place in Medicine, you may end up with a degree that is not useful for your future, and a waste of several years of your life.
The median age of students entering graduate medical programs in Australia is 25.4 years. By that age, you would have completed your medical degree and probably working as a Registrar in your chosen specialty if you choose the Year 12 entry (UCAT) route. Imagine entering medical school at 25 via graduate entry, then trying to study for the specialist training exams in your early thirties with a family to care for!
Further, when you apply through the graduate entry pathway, you can only apply to one university (with only three preferences) and you will be interviewed only by one university. The universities have colluded to make it this way, so that it is less work for them and easier for them to select students (although it imposes harsh restrictions on aspiring doctors).
Some people think universities are education oriented organisations, but in reality they are massive businesses with annual income of each university around a billion dollars - they earn about $30,000 per year of study at university for each student they enrol (about $10,000 from you, and the rest from the government, which evetually comes from your taxes). This means that the longer you study at university, the better it is for them. This is the reason why some universities are moving towards graduate-entry medical programs. It is to increase universities' income, not because it is good for you! Furthermore, universities are prohibited from charging full fee for undergraduate medicine, but they can charge full fee for graduate medicine!
With the higher debts of graduate entry and the uncertainty of whether you will get into medicine, universities will be laughing all the way to the Bank, but you will end up in the classic wheel of borrowing to pay for a degree to get a job to pay off what you borrowed (if you don't get into medicine).
Some people feel that they want to go to so-called "prestigious" universities (eg. Sydney University) which offer only graduate medicine. However, unlike other disciplines such as law, in medicine it does not matter which university you graduate from.
Perhaps 15 years ago, when GAMSAT was new, it was easier than UCAT but now most medical students who sat both tests claim GAMSAT is harder. GAMSAT is getting much harder for several reasons (eg many professionals wanting to change careers, the 'late bloomers', many school leavers putting off the hard work and the difficult decision).
Another important reason: It has been well documented that there is a general decline in psychometric test performance as a person advances in age. For eg, see "Socio-economic predictors of performance in the UCAT": Puddey and Mercer, BMC Medical education, 2013, 13:155. This shows that performance of candidates sitting UCAT between 16 years and 45 years consistently drops with age. So you are far better off sitting the test as early as possible (in year 12).