For any two given urban areas, their relationship is likely to be eitheras peers, that is, one competes with another (for labour, capital, and foreign trade), or as distinct members of a regional hierarchy (e.g., commuter suburb and commercial hub). And yes, depending on how you scope out regions, they may have different comparable roles. Note too that two suburbs within a given hierarchical region, say, Silver Spring, MD, and Arlington, VA, compete amongst one another within that region (Washington MSA).
In the case of Boston and NYC, you'd almost certainly see most transport and commute patterns within either city, with the inter-city transport being considered non-commute, for the most part.
More generally, this is why transportation networks almost always have to be designed, scoped, planned, and financed at least one level above the nodes they connect. Rome centrally managed highway construction throughout the Roman Empire, rather than leaving the decisions to local colonies and cities. In France and England, the first constructed transport systems, canals, were largely overseen as matters of national policy (though with private involvement), as was the Erie Canal in the United States. Development of railroads typically evolved similarly, with buildouts within specific nations in the US and Europe. This lead to a far more integrated system in the US (and USSR) given their much larger geographical area, whilst Europe's freight rail system remains much less capable than that of the United States.
For any two given urban areas, their relationship is likely to be eitheras peers, that is, one competes with another (for labour, capital, and foreign trade), or as distinct members of a regional hierarchy (e.g., commuter suburb and commercial hub). And yes, depending on how you scope out regions, they may have different comparable roles. Note too that two suburbs within a given hierarchical region, say, Silver Spring, MD, and Arlington, VA, compete amongst one another within that region (Washington MSA).
In the case of Boston and NYC, you'd almost certainly see most transport and commute patterns within either city, with the inter-city transport being considered non-commute, for the most part.
More generally, this is why transportation networks almost always have to be designed, scoped, planned, and financed at least one level above the nodes they connect. Rome centrally managed highway construction throughout the Roman Empire, rather than leaving the decisions to local colonies and cities. In France and England, the first constructed transport systems, canals, were largely overseen as matters of national policy (though with private involvement), as was the Erie Canal in the United States. Development of railroads typically evolved similarly, with buildouts within specific nations in the US and Europe. This lead to a far more integrated system in the US (and USSR) given their much larger geographical area, whilst Europe's freight rail system remains much less capable than that of the United States.