Advanced chemistry or biology?

Hello,

I'm a student currently in 10th grade. I have to finalize my courses in a week, and I'm still undecided between biology and chemistry. I really like chemistry and have always had good grades, as well as in biology. However, I need a very good high school diploma for my field of study. Where is it easier to get 13/14 points? Generally speaking, I'm good at memorizing, but I'm also good at arithmetic and comprehension. I'm actually equally interested in both subjects. My concern is either that I won't understand anything in chemistry, or that I won't be able to keep up with the material in biology and won't learn enough. What would you say?