While I have connected a great deal at MSP and DTW (DTW is great, btw, not sure why MSP is so special), keep in mind my perspective is a Bay Area one. Flying out out SJC in this example, NW has two flights a day, and most people don't even know who NW is, or where they fly. So while the infrastructure may be better, access to that infrastructure is actually worse, as NW's reaccommodation in the event of an irregularity may not be as good.