Are you planning to do an extremely time-consuming major (such as engineering) or need to graduate in 3 years for some very good reason (such as very limited finances)? If yes, then using AP credit to pass out of coursework may be an ok decision.
If not, then the decision is pretty easy. When you apply to medical school, you will see that:
1) it is very annoying, stressful, and extremely time-consuming
2) GPA matters A LOT
So your choices are:
a) Stay in this class, maybe relearn some material, maybe even learn some new stuff. If it is as redundant as you think, then getting an A should be very possible. So when you apply for med school, you have an extra A (see #2 above: GPA) and you don't have to waste time calling every med school you apply to in order to figure out if you can apply there (see #1 above: extremely time consuming application process).
b) Use your AP credit to pass out of the class. If your school is like mine, AP credit does not factor into GPA, so your GPA gets no help. And, there is the off-chance that you may find yourself less prepared than you thought for your first upper-level course, and end up with a B or even a C. And of course, you will still have to check with every mad school about AP credit.
When I was in your position, I had an AP score of 5 and chose option (b) above for Biology. I got my first C in that upper level class (and it wasn't even so "upper").
For Chemistry, I chose option (a). I got As in Chem 1 and 2, and when I ended up with a couple Cs later on, those As really cushioned my GPA from a disastrous fall.
So my opinion is save yourself the stress and uncertainty later, take the class, and do well! If you plan things well, there should be no reason why you can't fit in all the classes you want and still graduate on time.
