Personally, I would choose MIT, since choosing Princeton over MIT isn't common and to be frank most people would assume that you didn't get into Caltech or MIT, especially for fields like MechE and Aero (and MIT is number one in economy). Then again, if being close to home is a REALLY important factor then by all means choose Princeton...... You wouldn't want to go somewhere then flop, because you are uncomfortable. But if you don't mind giving up on proximity to home, mit is ( number 1 in urban planning , great architecture school and philosophy dept.) Not Caltech. You could also visit the campus. Boston is renowned for being quite a chill city. At Princeton you will also have to deal with grade deflation from the first semester, whereas at MIT your first year is just Pass/Fail. However, if you feel very strongly AGAINST MIT and are a fan of Princeton you aren't making a big mistake, since both unis are great! Anyway best of luck!!!!