They get compared a lot, but the fundamental difference between them is obvious. Neil sings from the heart, tells you about his life. Bob sings from the position of an omniscient observer, diagramming the situation with masterful clarity as though reality was a book he was in the process of writing. 'Course that alone isn't a big enough reason to like one or the other more.
Both are favorites of mine, but Neil's in a league of his own. When Bob's on, he's freaking on, he's unbelievable. But a lot of his stuff leaves me cold.