There are likely unique combinations of factors to consider in this type of evaluation for every city pair - including the distance between the cities, the presence or absence of high speed and/or low cost transit options between the cities, and the relative size. This is a topic that interests me both from the perspective of a long-time resident of Milwaukee and as a long-time fan of the City of Chicago.
I was intrigued by Aaron’s recent post “ Don’t Fly Too Close to the Sun Piece” which focused on the relationship between Milwaukee and Chicago and the notion of whether “proximity to Chicago or another mega-city represents an unambiguous good,” or - as posited by Aaron - may actually be more of a curse than a blessing, and something that drains vitality instead of increasing it.