For october, should I take Chemistry subject test (took class last year) or physics (AP this year)

As the title says, I am wondering if I should take the chem or physics subject test. I was originally going to take the chemistry in August, however I am going to retest on the SAT. Now, considering I am taking AP physics my senior year, and also considering my previous chemistry class did not seem efficient enough in covering test material (I am currently in the process of reading the whole barron’s book in order to make sure I know everything), I feel like scratching studying for chem and beginning to study for physics will benefit me more. Right Now, I just started unit 4 (There are ~ 13 units) in the barron’s book if some were wondering how far I’ve studied.

Oh, and my physics class is C: Mechanics