So if I would like to achieve a high study score and the course that I want to get into is business/commerce, should I try another subject?
You need to remember that VET is for trades and 'hands on' disciplines such as IT and Business. Students usually choose VET because they want something different and are keen to learn practical skills in that discipline, as opposed to learning just academic content. If you planned on opening your own business (for example), VET Business would probably be a good idea. The focus is on practical skills rather than academic knowledge.
VET -
Vocational (hands-on, doing) Education and Training.
It's really up to you - I would encourage you to pursue the VET if you are seriously interested in it. The fact is, you are more likely to do well in subjects that you have an interest in, rather than pick and choose based on scaling.
Have you had a chat to your career counsellor at school about this? I think you need to do a bit more research into VET before making a decision to pursue it or not.