What BS degree best prepares you for the Air Force PA Program?

You would be well served by a minor in biochemistry; both for the amount of basic science and a taste of the volume and type of study you will need to complete in pa school. That said, the degree itself does not matter as long as the school prerequisites are fulfilled and you did very well in those classes. Better to have A’s in prerequisites with no more science classes than a bs biology with a 3.2 science cum.
My ba in English Literature worked for me. Good luck.

MINIMUM EDUCATION
Master of Science (MS) in Physician Assistant studies (or equivalent Master's degree/Doctorate) from an ARC-PA accredited institution

I am an"old school" PA, and don't have a clue what they look for these days. Sorry I can't be of any help.