Lifted from Comments: My Friend Leslie Appleton-Young writes:

In 1996 E. Digby Baltzell published a book that addresses some of the differences between the two cities going way back -- Puritan Boston and Quaker Philadelphia. Here is an excerpt of a review.

Digby Baltzell uses the history of Philadelphia and Boston as very real examples of two types of leadership. In Boston, the "Boston Brahmin" elites formed a strong upper class that was not tolerant, certainly, but took responsibility for community life and exercised a tremendous influence on American culture, politics, arts, and science. In Philadelphia, the "Proper Philadelphians" were charming, tolerant--and deeply irresponsible, abandoning any role in governing the city and making it by common agreement the worst run city in the United States. When Philadelphia needed a mover and shaker, it imported some one from outside, like Ben Franklin.
Baltzell takes these difference back to the colonial period and the dramatic differences in the viewpoints of the Puritans who founded Boston and the Quakers who founded Philadelphia. He also sees these changes working forward as the old upper-class socialize immigrant elites into their respective patterns, producing the Kennedy clan out of Boston, and Grace Kelly out of Philadelphia. Many of the points here can also be seen in David Hackett Fischer's Albion's Seed.

Then again, given a choice between getting to have dinner with Grace Kelly and getting to have dinner with Joe Kennedy, I don't think it would be a tough choice...