<p>I got the impression that it was easier for colleges to accept AP credit because it’s standardized. To accept transfer credit, they have to evaluate each class to figure out if it corresponds appropriately to any of their classes and so on. For the small number of true transfer students, they will do this, but for the larger number of freshmen, it seems many schools do not want to bother. Obviously schools that already have a relationship with the school where you took the course would be most likely to accept the credit.</p>