i'm not making your choice for you. [insert irked rant about people who phrase their questions as demands]
i know nothing about penn, except that a graduating friend from philly is now (surprised at herself, but) returning to penn. but she's in math, and a grad student. i'd argue that boston trumps pretty much anywhere, as a city with an incredible number of college students. look around, there's plenty of threads on the atmosphere (hint: work damn hard, party even harder), the campus (i don't think it's ugly here, but i also don't really care, and as noted, i like boston), and all sorts of reasons to go here; if you have more specific questions, ask, but i suggest you look around. what're you interested in studying?