Dual credit courses are by far more likely to be accepted by medical schools/you won't need to retake them (I can't think of any reason you would need to retake them).
APs on the other hand, as ppl have stated, are difficult, often not taught well, many ppl dont get the AP credit, colleges may not accept it, and medical schools tend to make students retake certain AP science classes
So, say you took Gen. Chem 1 as a dual credit class, you won't need to retake it, whereas if you took AP chem, many schools would make you retake gen chem/take an upper level chem to compensate
Go dual credit. I wish I had, but unfortunately I was unaware of such things as a high school student.
Make sure you work hard though! In dual credit you will receive a letter grade, which will affect your college undergrad gpa, so try to start off on a good note