AP World History = ridiculously easy.
AP U.S. History = more detail-oriented, but you will be just fine if you regularly read throughout the year.
AP European History = definitely the most challenging. It requires just as much knowledge of detail as APUSH, if not more, and is more demanding when it comes to essays - APUSH’s essays were a joke, at least when I took the exam (2009).</p>
As a side note, history is one of my stronger subjects, so perhaps my post is colored by an excessive subjectivity.</p>