[Crawford]

As your pictures show, the Bronx is generally significantly denser than Brooklyn, even if the overall density is roughly the same (because Bronx has far more parkland, highways, industrial and other nonresidential uses).

And it isn't really the South Bronx that has that 5-7 floor tenement typology. It's more like the entire West Bronx (whether South or North). If anything, the North Bronx is probably a little denser than the South Bronx (though that may be changing because there's more newer infill in the South Bronx).

The big built form distinction in the Bronx isn't between North and South; it's between East and West. Basically the Eastern third of the Bronx has a less dense built form and the Western two-thirds have the typology shown in the pics.

The rough border between "dense Bronx" and "not so dense Bronx" is the Amtrak NE Corridor line, though the density starts to slowly decrease east of the Bronx River.