I did AS Maths , Physics, Chemistry and Further maths(retaking) and got AAAC respectively. I found AS Chemistry easier in a sense where the content wasn't as hard to understand as physics, however I personally found it very content heavy and had to memorize a lot. The AS Chem exams are easy but easy to make mistakes so to get an A involves a lot of revision, practice and precision. AS Physics I found a lot harder to understand but my interest in the subject made me willing to go that extra mile to understand the content. With the physics exam, it is very hard because you have to apply knowledge to very random situations. As a result low grade boundaries. Oh yeah and being good at maths doesn't make you good at physics.
But chose what you enjoy more. If you are having second thoughts about physics that is a good reason not to do it. physics is lyf lol. Good luck in September, hope this essay helped