Computer Science is the only department at Princeton which offers both A.B. and B.S.E. degrees. Here, we outline some of the key differences between these options. TLDR; don't stress over it; in most cases the differences are minimal.
As outlined on the requirements page, there are a few differences between the courses required of A.B. and B.S.E. Computer Science majors. Students seeking an A.B. degree are not required to take the engineering prerequisite such as physics and chemistry, and also have to take one less math course. A.B.'s only need to complete 32 courses rather than 36 over the four years. On the flip side, A.B. majors are required to participate in four semesters of independent work (two junior year and a year-long senior thesis) and these do not count towards the 32 required courses. In this sense, the total course load is relatively similar between the two options. B.S.E. majors are required to perform one semester of independent work.