Well what I did was take AP Chem dual enrollment through a local university and got A's in Gen Chem 1 and 2. If this option is available to you for either calc or chem and you are sure you will get and A do it.
Pros: Don't have to take it in college, counts towards your GPA
Cons: If you don't do well in it, it still counts toward your GPA.
If you can't do that, and you find the material to be easy, take the AP test. If you have a really good comprehension of the material, there really is no need to take it again in college.
The third option would be to take the class and take it again in college. If you want to go this route, don't take the AP test, it would be a waste of time.
For Calculus, some schools will let you move on to calc 2 without taking the AP test and give you credit for Calc 1 when you finish the course. I'm not sure but I think that it costs more than the AP test to do that.
Also, this is just my opinion, I'm sure there are a lot of people that would tell you to retake for the easy A. So essentially, it all comes down to whether you think it's worth it or not.