At Brown, almost every class you take will be taught by a professor, not a graduate student or adjunct. I don’t know what Northwestern does in this regard, but among the Ivies, Brown and Dartmouth have the most undergrad-focused programs. For example, the undergrad teaching assistant program is a unique feature of the Brown CS program; it will give you the opportunity, if you get one, to assist the professor in teaching the class, mostly through help sessions, grading, and one-on-one meetings with the students, whereas at other schools this role is taken by graduate students. The UTA opportunities are highly coveted and have rigorous interviewing processes, but there are also a lot of them out there. One introductory class had to hire over 25 UTAs for the class. This is just one facet of the CS program at Brown, which is very well regarded in Silicon Valley, but it is an important part of how Brown teaches.