I studied engineering at Princeton and went to grad school at MIT. Both are outstanding universities. I will attempt to provide some of my experiences at each university.
Pro features of MIT
MIT has the best engineering school in the country. There are more engineering students, more engineering professors, and more engineering courses. There is more of most things in ChE at MIT. His roommates will probably be studying STEM. Some of the liberal arts courses are far better than most people understand. Boston is the best college town in the US. MIT’s engineering contacts are outstanding. There are more MIT engineering alumni than Princeton engineering alumni.
Frat culture is alive and well at MIT.
Similarities
ORFE are very good at both universities. ORFE is a very popular major at Princeton; the Sloan School has been a leader in the field. Employ-ability is probably a wash. Tiger Trek is a sponsored trip to Silicon Valley to visit with companies such as Apple, Facebook, Google, Khan Academy, Telsa Motors, Twitter, Square, Juniper Networks, Hewlett-Packard, and several venture capital firms. Possibly more Wall Street at Princeton and more aerospace at MIT. Grad school acceptance would be similar; however, a student that loves MIT or loves Princeton may do better academically at that school and receive better faculty recommendations for grad school.
Pro features of Princeton
Princeton is focused on providing the best undergraduate experience in this country. The quality of the engineering professors and the quality of the engineering courses are very similar. Engineering education at Princeton began in 1875. The National Research Council has ranked Princeton as having top PhD programs in Chemical Engineering, Civil Engineering, Electrical Engineering, Mechanical Engineering, and Computer Science. At Princeton his roommates may be history majors, economics majors, public policy majors, and a STEM major. Princeton students love their on campus activities so much that they mostly stay on campus. Many Princeton engineering students start their careers as engineers and are promoted into general management positions. The MIT campus looks like it was designed by engineers; the Princeton campus is gorgeous and has many buildings designed by world famous architects. The Princeton campus has dozens of art sculptures around the campus to make art a part of campus life. Since Princeton is half way between the United Nations and Washington D.C. world leaders are constantly giving lectures on the Princeton campus.
The strength of the engineering program at Princeton is that STEM is very strong at Princeton AND students can take outstanding courses in philosophy, the classics, history, sociology and other liberal arts subjects. Google CEO Eric Schmidt discusses his reasons for attending Princeton over a STEM university in this video: https://www.youtube.com/watch?v=o0gtoWwx5Is Half of Princeton students change their major; the variety of strong majors entices students to switch to a new field.
Fraternities are a minor factor at Princeton. One-third of the students choose not to join one of the upper class eating clubs. There are substance free dorms. Your son can find many activities that do not involve “partying” or alcohol. Murray Dodge has free chocolate chip cookies at night.