pros
/F/H
Is that really a pro?
cons:not as diverse as Yale (at least this was my feeling during preview), on-campus housing is virtually non-existant, having a car is such a hassle
any thoughts about anything on this list?
I'm really not sure how to compare diversity, but for your other points.
On-campus housing does exist and you may elect to take it. In some classes a handful live in Sansom Place East and in some nobody lives there. The thing is that Philadelphia's housing near campus is much cheaper and still safe that nobody chooses to live on campus. This isn't a school where the students are scared to, can't afford to, or can't live near campus, so they aren't huddled in on-campus housing.
Still you really have several choices for living locations and I'll try to blow through them quickly. I feel like the MD/PhD program for some reason is doing a poor job getting this information out there, and I think they're going to try to put more out for revisiters next year.
Center City - The majority of MD/PhDs live here, mostly in the 18-20s up to the river from South to Race. I live for example near 23rd and Locust, which I'd say is where many Penn grad and med students are concentrated. You are correct that owning a car here is a pain for a few reasons. First is, as Philly is becoming a much more happening city, rents are going up quickly and dramatically. Our stipend, which has also been increasing quite a bit over the rate of inflation the past few years, allows us to live decently there. But, it's probably not going to be possible to afford both a 1BR apartment and a car on your stipend without serious budgeting. The second reason is that street parking is really difficult there. You'll need a permit to hunt for spots, which requires you to change your license and insurance to where you're living (probably raising you car insurance rate), but even so the population density is high enough that street parking is hard to find much of the time. But, if you want to pay for parking it's pretty expensive >$200/mo.
University City (the east of West Philly) - A sizeable minority of MD/PhD students live here. By my estimates, a larger proportion of MD students live here and a majority of the students in my graduate program (most of which can't imagine why you'd choose to live in CC) and many other professional schools. This part of town is more residential, has less tall buildings, feels more like a neighborhood, and is cheaper. Street parking is available here and since rents are lower you can afford to have a car.
Now there are many other options depending on how you want to commute.
You can go further north on the east side of the river and call it the art museum district. The mass transit options up here suck and are non-existant to Penn so you'd have to walk or bike. Street parking isn't so bad up there.
You can go further south in CC and you end up around Gray's Ferry or Graduate Hospital areas, which are "transitional" (read: not so nice) areas where many students live because it's close to CC, close to Penn, and cheaper. I wouldn't recommend it simply because they're going to demolish the South St bridge soon, adding at least 15 minutes each way to any walking. Street parking again isn't so bad.
You can live east of broad and have a more diverse, lively urban environment (maybe even cheaper than the parts of CC I was describing earlier). You can subway or bus in from these locations and I used to live over there myself and loved it. Street parking there though is also non-existant.
You do have more options, but what I just covered is probably where >95% of the MD/PhD students live. I hear an occasional student who commutes in by train or car from the burbs (like most of the staff/faculty), but that's kind of rare. The subway/El stops at 34th and Market, which is only 6 blocks form the med school, so if you don't mind a longer commute you can live anywhere on the subway routes around the city.
I know to the average incoming student the response is that the students are so scattered. In reality, not really. West Philly and CC are separated by a river. All of center city is only about 2 miles wide. University City is on the order of the same size if not smaller. Since most of the students are close to Penn, this means most of the students live within 2 miles of each other.
The question that everyone is going to ask you is: why have a car? Yes Philly is not NYC, but I'll make the comparison anyways. If you lived in NYC would you want a car too? Philly is large and in CC everything you'll need is in walking distance. Mass transit (subway and/or bus) will take you anywhere in the city. I rent a car when I need one, which is easy for me to say cause I'm over 25, but really I have no desire to own a car. But, since most of the MD/PhD students live in CC you've probably heard this perspective already. The UC group wonders why more students don't live over there and will tell you it's okay to have a car there.
In the end Philly is such a big and diverse city that you can get whatever you want for living as long as you can afford it. Penn is situated right on that border zone between the big city and the residential areas that further enhances you ability to make choices for living (e.g. Jefferson is smack in the middle of the big city, while Drexel is almost in the burbs).