[NativeNewYorker]

The blue collar apartment hives of the outer boroughs have always been an unpleasant first step on the American dream ladder. I know, because I grew up in one.

The non-slum outerbourough neighborhoods like Forest Hills compete with Manhattan for the upper middle class, and former slums like Williamsburg are now very chic.

I've actually spent a lot of time in Flint, and visit Philly often. Both are stagnant pits. Cheaper than NY? Yes. Shorter commutes and lower taxes? Yes. But pits with scant upside for folks looking to improve themselves.

[Clemenza]

It may be politically incorrect to say this among certain people, but a major advantage that New York had over Philly and Cleveland (to say nothing of Newark) was that the very rich stayed in the city in the former. In Philly, as early as the 1910s, the wealthy were leaving the city in droves for the Main Line, while those in Cleveland went to places like Shaker Heights.

The old journalistic cliche is that the cities needed to maintain the "blue collar middle class" to survive. Well, Philadelphia did remain a blue collar city well through the 1980s (unlike Detroit and Newark, which saw a massive flight of such folks after the riots), but it could never stem decline as New York did due to the lack of a large number of wealthy folks remaining in the city.