Sure there's in between sizes, but the population willing to commute to a suburb of NYC is also small relative to the city proper; as is the population availabl

Sure there's in between sizes, but the population willing to commute to a suburb of NYC is also small relative to the city proper; as is the population available to a mid-size city (which may have commute time problems of its own and doesn't have the employment draw of the hugest cities). And people may both move irrationally in search of employment and move rationally despite huge commute times (if the greater chance at a higher income outweighs the commute time for you). Or you may move based on rational principles but incorrect premises about how long you'll have to commute. Or move despite a long commute with the expectation that working in the city will give you chances to advance in your career and soon be able to afford a shorter commute.