My D1 had a similar dilemma and decided to take Calc AB so she could also take Principles of Engineering. She wanted to get a broad background in the different types of engineering before committing herself in college, so she felt it was worthwhile. She is considering self-study to be able to take the AP for Calc BC.
You are in even a better position than she, since CompSci is a more rigorous course. As one of the other posters mentioned, you can always indicate on your applications that you took AB because of a scheduling conflict.