This year, the Physics HSC exam was easier IMO, so Chemistry will probably scale better. But they are usually on par with each other regarding scaling each year (Chemistry is usually SLIGHTLY higher, but it wont make much of a difference). Overall, I found the Physics course harder to get your head around, but Chemistry has ALOT more content.
Both have options that sort of cover medical fields, like medical physics or forensic chemistry. It really doesn't matter. Just do what you enjoy the most, because I've been told alot of what you learn in Physics is 'wrong' or extremely simplified compared to what you will learn in Uni.
And what ones more enjoyable depends on who you are. I found chemistry alot more enjoyable because I found it more relateable to real life, rather than all of this atomic theory in physics that was all hypothetical. The majority of the physics course (Ideas to Implementation and Quanta to Quarks especially) were pretty heavy on history and developments, so I didn't find that very intriguing. Chemistry was just more interesting, for me anyway.
One things for sure though, Biology is shit