I agree with NE2000 and ninwa, I did all three sciences in VCE, bio was definitely hardest for me and physics was by far the easiest. I think this is because there are just so many varied application questions you could be asked in bio which require an indepth understanding to even partially answer. At my very, very average government school (read: mean 30, 8% scores > 40), physics is almost unanimously seen as being markedly easier to both grasp and do well in than the others. And of those few who do both chem and physics, they general consensus is that they prefer physics, although a couple of people have said this is solely due to the relative difficulty of the midyear exams. Personally, I don't really have a clear favourite, I enjoyed aspects of both this year, but if I had to choose, I'd say physics, it comes easier to me and I would like to continue (or properly start, depending on your opinion of VCE physics) to study it.