I would choose based on teacher reputation. At my kids’ high school, AP Chem was poorly taught, and the only way anyone ever did better than a 2 on the exam was through intensive self-study and/or tutoring. (Everybody loved the teacher as a person, but even students who aced the class did poorly on the exam.) AP Bio, on the other hand, was well-taught and had a high pass rate on the exam.
They’re both challenging classes when taught properly, and both valuable. See what you can find out about the teaching and the pass rates, and choose that way.