Here are a few of the impressions I have gathered about the contrasting characteristics of these twin cities.
Minneapolis: Gotta get to work on time! St. Paul: I'm late for work but it's no big deal.
One antique dealer I talked with characterized the different vibes in the two cities this way. Minneapolis: black shoes, black suit, silk tie. St. Paul: brown shoes, corduroy sports jacket (with elbow patches), wool tie.
As noted elsewhere, Katharyn has formed the impression that St. Paul is more interested in preserving its history, in the form of historical buildings, than Minneapolis is.
These twins may be more fraternal than identical.