Going to a lower-ranked school for better advisor fit
All of the schools that you are discussing are first-rank computer science schools with global leadership in their areas of specialty.  In this area at least, the only real difference between the "top" and "top of the top" schools that you are considering is the number of different areas in which the school is a global leader.  Thus, if you already have a clear, narrow focus that you know that you want to work in, and there are 1-2 people in that area at all of the schools you are choosing between, the distinction between "top" and "top of the top" is pretty much null.  

Furthermore, your graduate career will be primarily determined by your advisor relationship rather than the school within which it will occur.  Beware of being misled by first impressions, but a good match with your Ph.D. advisor is worth much more than the incremental difference between schools.