You've definitely experienced some version of this conversation:
"Oh you're going to Penn? Isn't Philly boring/terrible/dangerous/dirty? Why not go to college in New York instead?"

Basically, you end up defending Penn (and by extension, Philadelphia). At least you aren't trying to differentiate two Pennsylvania universities from each other (or the third lesser known Indiana University of Pennsylvania). 

So, here are the main differences (both good and bad) between Philly and NYC.

(1) Food
Philly: It's really catered towards meat lovers (e.g. the cheesesteak rivalries) or "quasi-meta" health freaks (e.g. half of 40th & Walnut). There are actually lots of great BYOB restaurants around, but you'll probably only end up cabbing to the same two every weekend. Also, brunch is a thing. 
NYC: Everything is offered, ranging from dollar pizza to the corner deli to normal eateries to prix-fixe dinners to a $10,000 diamond-studded martini. There are also more places open 24/7, and the bagels are the best.
Winner: NYC

(2) Weather
Philly: Hot and humid summers, mild springs and falls, and cold winters. Rains year-round and snows occasionally. 
NYC: Warm and humid summers, unpredictable springs and falls, and cold and damp winters. Fun Fact: Manhattan ran out of snow boots this past January. 
Winner: Philly

(3) Crime (& Safety)
Philly: Penn/Temple/Drexel consistently top the most dangerous college campus lists. The DP front page also frequently mentions some recent shooting/robbery near campus.
NYC: From what I've learned from Suits, I'm pretty sure insider trading and dirty deals are illegal. I've also heard that Central Park at night has changed from its depiction in Home Alone 2: Lost in New York (i.e. less sketchy). 
Winner: NYC

(4) Sports
Philly: Pretty sure people care mostly about the Flyers and the Phillies because Eagles fans are likely incarcerated/intoxicated. Philadelphians and its suburb friends are very much into sports (i.e. Sundays are days for wings, chips, and salsa). 
NYC: They have 2 teams in the MLB, NBA, and NFL. That probably means that they're really great or they aren't, so New Yorkers need a rivalry to actually care about sports.
Winner: Tie

(5) Attractions
Philly: You can be a tourist in Old City and stand in line to stare at archival artifacts that may have been forged by Nicolas Cage. However, Philadelphia's museums are what defined my childhood growing up in the suburbs (e.g. Franklin Institute, Please Touch Museum). The Philly Zoo is always a good time as well. For more refined tastes (e.g. opera, theatre, etc.), you might have to dig a bit deeper to find the real gems. 
NYC: Historic and landmark buildings are scattered throughout the city. Central Park is quite a feat itself, and there are tourist destinations all over Midtown. And of course, everyone loves the discount same-day Broadway tickets at the TKTS booth. Beyond the tourism industry, the city features various neighborhoods, each with its own personality and highlights—you're sure to find at least one venue suiting your tastes. 
Winner: NYC

Philly: 1, NYC: 3

Perhaps Philadelphia does have an inferiority complex compared to New York, but our beloved City of Brotherly Love (get it?) certainly owns whatever stigma it may hold. Not to worry, most of you will likely end up I-banking in New York anyway. Some of you will ironically (or not) buy the overpriced "I ♥ NY" merchandise in Times Square. And for the others, maybe just bursar some Penn gear from the bookstore to validate choosing Penn, not Philly.