<p>The overall US News rankings are a useful convenience in identifying clusters of reach, match, and safety schools (including places you may never have considered). They are not a good basis for distinguishing schools within those clusters. It would be silly to choose the number 10 school over the number 15 if you like the latter much more, or maybe even over the number 30 if that one is much cheaper, or has something specific you want. </p>
<p>I don’t know where you are getting your department rankings. There really isn’t any good basis to precisely, accurately compare undergraduate department quality in isolation from overall school quality. You can look at graduate department rankings to get some idea of faculty strength and research productivity, but at the risk of overlooking some excellent schools that don’t even have graduate programs, and may offer superior teaching.</p>