It really depends on how the class is taught. AB calculus isn’t terribly difficult for students who have passed prerequisite classes, and average students will be fine. BC calculus is still fine for average students who have passed AB calculus. When AB and BC are combined, it can be a bit much for average students.
For most students, AP calculus is harder when it covers integration and related topics. If a calculus class only covers differentiation, then it is often easier for students than AP statistics. It mostly boils down to how much of the math can be solved systematically vs how much requires broader thinking.
The topics in AP Statistics are not especially hard for your average math student. Most of the math is based on algebra, and most states require competency in algebra in order to graduate with a high school diploma. That said, some instructors might intentionally make the class difficult, which can be prohibitive.