Don't worry so much about scaling, it only plays a small part in calculating your final marks. Focus more on interest. You're more likely to succeed in a subject you're actually interested in.
I found that physics was the easier of those two science subjects, but if you don't like maths, then it's probably not for you. Chemistry has some maths (mostly algebra based), but not as much as physics. I found that some of the concepts in chemistry hard to understand at first, and I didn't completely understand some of them until right at the end of the course.
I did Legal Studies in HSC, and found it was mostly just a way to get easy marks. The course content was interesting enough, but I'm probably not going to end up using most of what I've learned now that I'm done with it. It depends on what you want to do after you finish the HSC.
Just go with what you think is the better choice. Don't choose a subject based on scaling, especially if you're not going to find it interesting or it's going to be hard for you to get good marks in it.
