The problem with any of these comparisons is that cities are very heterogeneous. In Boston, the Back Bay != Roxbury and in NYC, the West Village != the South Bronx. However, at least absent a doorman, I probably wouldn't leave a door unlocked or an accessible window ajar the way I routinely do in my (only) semi-rural home in New England. When I visit people in cities, I have to consciously remember that they'll be unhappy if I am casual about such things like I am at home.