I think people consider repeating year 12 a better route than transferring at a later date because they do not fully understand how university works. I have a feeling that these people believe they would effectively be wasting a year at uni studying things they did not wish to study, this is not really the case.
jackfrost, you do realise that a degree is obtained through the attainment of credit points through the completion of various units, which may be taken by anyone, regardless of the degree they are enrolled in, so long as they meet the relevant requirements. What this means is that people in different degrees often take the same units, especially in first year.
If you decide to go for the transfer option, you simply pick units required for the degree you wish to transfer into, and then transfer the credit points attained from these units over when you do eventually transfer into your desired degree. You effectively end up doing the first year of your desired degree under a degree of a different name. No time wasted at all.
It is not worth repeating year 12, you will hate it. University is incredibly flexible, once you're in the system (regardless of what degree you start off in) you have so many options. Don't view transfers as a long, arduous waste of time, they are not.