I always felt that the undergraduate courses (at least the split level courses I took) were more demanding in terms of time (not necessarily effort) because generally they had lots and lots of homeworks where you need to read a book and write answers from them. And of course grad students are supposed to do a lot more than the undergrads in the same class. But in the graduate courses, you will need to put more effort as it is more of literature reviews, projects, reports etc. The good part though is generally less homework and sometimes no exams as all...