Disclaimer: I have a Penn affiliation.
That said, the MSTP at Penn really rocks. Well organized, well funded, well staffed both administratively and PI-wise. Penn is perhaps the most collegial institution I've ever experienced (and I've been at a few, including being a student at two MSTPs - long story). Almost everyone there is very happy to share/educate/generally be nice. The majority of students are NOT highstrung (every place has some, though). Lastly, I'm from Boston and was raised to dislike Philly. That said, I've loved living here. Center City (which you unfortunately don't see during interviews usually - a freakin' crime considering how nice it is by comparison to W. Philly) has become a small version of the nice areas in Boston. I can't help but wear the salesman hat as I truly believe the experience here outstrips what is available at many other institutions.
As far as E. Coasters being throats, not so. There are some in every med school class, but not more here. In fact, a whole lot of the students here are NOT E. Coasters at all as Penn draws from around the country.
btw, Neuronix, I'm a neuroscience PhD candidate (though not for much longer as my thesis gets handed in TOMORROW) and assume from your name you're interested in the area (no?). Happy to talk if you'd like.
Best of luck with the decision. Sorry I can't say much about U-dub other than I've heard it's a very solid program (my boss was offered a chairmanship there and turned it down to stay at Penn before he even had come up for tenure - that says something about what this place is like, I think).
Cheers,
P
