Most comparisons of cities are offered as a way for the speaker - usually an inhabitant of the smaller or less lively of the two cities being compared - to make a display of worldliness and, in doing so, reassure him or herself of the wisdom of winding up in the smaller or less lively city. It's a human phenomenon, as common in Paris as in Boston and San Diego. One also hears it constantly from any New Yorker who has ever chosen to settle elsewhere.*
But, as Italo Calvino hints in his book Invisible Cities, in which narrator Marco Polo describes a seeming infinity of exotic metropolises that all turn out to be Venice, cities might more accurately be considered closed system unto themselves, incomprehensible to outsiders. Narrator Marco Polo's descriptions exceed the imagination his interpellator Kublai Khan, and indeed of the reader. It's impossible to accurately judge one city by the scale of another.
So far, the greatest benefit I've derived from this way of thinking is that it has permitted me to love Le Mary Celeste, an oyster bar some good friends recently opened in the Marais.