My brother is a D4 at Tufts and would've loved to go to Penn, had he gotten accepted. It honestly depends on you, but here are my thoughts. I think I would have to disagree about Philly being less fun then Boston. Philly is 1-2 hours from NYC and can be a fun destination for 3 day weekends, whereas Boston can get pretty boring and the cost of living is so expensive (food, bars, etc.). Philly has a lot of restaurants that are underrated but deemed one of the best places if you're a foodie or just want to try different cuisines. After spending last summer in Boston, I found myself getting pretty bored and also heard police sirens every night (I lived by BU's undergrad) so I think it all depends on what part of Boston / what part of Philly we're talking about. At Penn, you'd be in University City most of the time and being around 12 other Penn affiliated schools is a great atmosphere/learning environment that to me, mirrors that of Boston.
The curriculum at Penn is a lot better than Tufts, so I've heard, and they've made some changes within the last year or two and have actually lowered the amount of tests per week (marginally, but still every test counts). The renovations are supposed to be ready for class of 2020 (our class) and that was a former problem that many people had with Penn, so that's one less thing to worry about now. If you know you want to specialize, or are even considering/leaning that direction, Penn will raise your chances immensely. Tufts ranks and especially in a class of 200+ (they're looking to increase the class size even more, they're planning on becoming more and more like NYU) it might be easy to be drowned out/out-competed.
You also have two good friends attending Penn and a possible mentor at Tufts -- but who is to say you won't find a mentor at Penn? Hope that helps