they are both fairly small jumps between 1/2 and 3/4 TBH, though from my personal experience chem was bigger.
In my opinion, chem and physics are about equal difficulty and are really similar in style. people on this forum bash physics hard because of the cheat sheet, but honestly you hardly even need a cheat sheet (I walked in to the exam without a cheat sheet
) if you thoroughly learn all the concepts involved (you don't need to memorise explanations because you can actually explain them). Chem might not have as many calculations as physics, but it still has many 'if you get the answer right you get full marks' questions like equation writing, naming/drawing carbon stuff etc.
what aspects with physics are you struggling with?
You've just demonstrated why we bash the cheat sheet. You can do the course perfectly fine WITHOUT a cheat sheet; why on earth does the exam need one? The course has LESS content compared to 2012, but more time to study for it (no more mid years to study for, can focus on more coursework). There is too much rote learning of equations and question styles and not enough actual physical insight. VCE physics doesn't, for instance, address why a person in uniform circular motion feels as if they're being push outwards when they're clearly not. Nor does it provide an accurate explanation for the stability of atoms (the Bohr theory of the atom, mentioned in VCE physics, does not work for anything above the hydrogen atom, which is something I fee students should be aware of at least).
The gripe lots of people have with physics is actually its repetitive nature and lack of substance. Lots of the course follows the form 'know this for the exam, know that for the exam, this is too hard for you'. VCE physics is far too watered down that most students previously enthusiastic about physics, like myself, become quite disappointed. Add to that the ridiculousness of not making maths a co-requisite for physics (I dare you to do first year uni physics without spesh) and the course becomes almost patronising at times.
Anyway, enough physics-bashing. Physics at uni is actually quite enjoyable, especially after you get through first year physics which can be a bit dry.
If you had a choice between physics and chemistry, then everything else being equal, I'd say go with chemistry. Chemistry is more necessary for uni requirements. Physics is only really needed for physics and engineering students; chem is needed for chem and all health science majors (health science is in a significant part applied chemistry). As EulerFan mentions, we need to know what you want to do later on in life first.