My D went to NU and my S is going to Penn and had been interested in Cornell. I also live in the Philly area.
I can’t comment on the academics as my D didn’t major in those listed, and my S won’t either.
I think the point about the midwestern view of NU is very well taken. In the midwest, NU is viewed very prestigiously.
But for location: I do agree that Penn’s location and NU’s location are somewhat similar as far as city-ish feel. Chicago is the bigger city, but NU is not in Chicago; it doesn’t feel like it’s in Chicago; it’s on a gorgeous lake in Evanston, a suburb. True, you can get to Chicago by train or by cab/uber–how frequently will depend on how much you want to go into the city and your own schedule. The physical site of NU’s campus is stunning - the lake is so gorgeous - although for pure stunningness I personally think Cornell is the most stunning. As far as the campus itself - architecture, buildings, lay out - I think Cornell and Penn beat NU.
For Penn–Center City is not the only place to go to in Philly. Philly has many, many areas and many different places to explore. Penn is not quite in the area of most interests in Philly, but it’s still in Philly as opposed to Evanston; and you can easily walk to places of interest, eg the art museum. Transportation on the Septa or Patco is easy, although I wouldn’t go on it very late at night.
No one mentions weather but I think Penn is the clear winner here, but I hate cold weather!
Social life is totally subjective. They’re all large schools with many opportunities to join clubs, meet people etc. My D was very happy socially at NU. Of the three, Penn is the most urban, then NU, then Cornell.