I’m in year 13 and still do both. I’m a tad biased since I’ve applied for a chem degree but physics is a lot more challenging, at least personally.
Chem isn’t as maths heavy and the calculations you do are very easy, whilst passing physics without doing a maths a level alongside it would be close to a miracle. The data sheets are quite different so the type of content you have to memorise is very different; all the formulas for physics are given to you alongside constants, and in chem none you’re given none, as you’re essentially just given a periodic table and some organic structures and spectroscopy data values. Practicals are very different too, physics based ones are mostly pendulums or ramps or circuits (all extremely exciting.....) while chem is a lot more involved, heating stuff, using chemicals not given to lower years, using fancier (well just a tad) equipment.
That’s just a few differences but if you have specific questions shoot.