I wouldn't worry if you're not quite sure yet, you've got plenty of time to decide.
Just don't base your choice purely on scaling of a subject, decide which subject you enjoy the most and ones which you will require for university admission. I'd consult your career's/ VCE advisor, and look extensively through the study designs to help you come to a conclusion. You'll also have a better idea when you get your mid-year/ end of year results.
In my personal opinion, I'd do biology, as it is an extremely interesting subject. Aquired knowledge in biology is great to have. But I'm completely biased. (biology is my favourite subject...)
My boyfriend did biology, chemistry and chinese, and he said he enjoyed Chinese the most as he has a passion for languages and had been learning it since prep (he got a 47 before scaling). If you are highly ambitious and work your butt off, you will do well in Chinese. Chemistry is a good subject if you are interested in it, otherwise it is hellishly boring.