Or would it be better to replace that class with an AP Chem/Physics?
This shouldn’t even be a consideration unless you’ve already taken, bio, chem, physics and one of those AP AND have 4 years of your other core courses (math, english, history, and foreign language). If you have room for this elective and it’s interesting to you, then sure, go for it.
Only if you have already taken (or plan to take) a year of bio, chem, physics, and an AP science. Essentially, Anatomy should be a fifth science elective option but not one of your primary four.
It is a good elective to take at the same time as AP Bio but it should not replace a core science.