I'd agree with your assessment of Market Square. However, I think Post Office and Tommy’s Park in the Old Port, and Monument Square, as well as Church Street in Burlington, come close. But you’re right, Market Square wins by more than a slight margin—it’s a wicked cool spot. Sometimes I wonder if it’s too cute for words, though, like a stage set (a la Exchange Street). This gets back to your point about liking a little bit of grit. I don’t know.
Tommy's Park slipped my mind, but it's definitely up there. Market Square is almost too perfect, but I can't actually find a way to put into text why that's wrong. But I do see what you're saying.
I would differ in the last list (urban dynamism). I think you’d get the first two right (1) Boston/Cambridge, (2) Providence, then I’m not sure. I don’t know a ton about New Haven, so maybe you’re right. But what I’ve heard is that it’s nothing compared to what it was, or what it could be. I’ve never heard anything good about it from anyone other than urban enthusiasts who look through rose colored glasses.
Which is precisely what I do when I got there. New Haven is the birthplace of the hamburger (Louie's Lunch) and home to the best pizza in the country (Sally's... though some prefer Frank Pepe's). It's tough to knock a place that really knocks two American culinary classics out of the park. It's home to Yale, it's right on the coast and has a lot of good architecture (including a great train station). I've also only spent time in New Haven as a visitor and have never experienced the down sides (high crime, good deal of urban poor). That said, as an urban enthusiast, I have no doubt that I could find a great place in the core of the city to live and be happy. Especially when I can take the MNRR right into Grand Central any time I want.
I think you’re right Portsmouth’s proximity to Boston gives it an edge in some respects, but then again that factor would only matter to people who value a larger city for its amenities. In that case, I think you get more out of Portland at only another 45 minute distance from the big city. In my opinion, this probably puts Portland—especially with its educational institutions and cheaper housing—ahead of Portsmouth.
I didn't really take education into account. But you're right, it gives Portland a big advantage.
This is all very subjective, so I think the only real way to rank a place’s comparative importance is by population. The numbers speak for themselves. But that gets tricky because of density and square mileage making it an apples to oranges comparison sometimes. Then, the metro area becomes a good proxy for population. I think comparing metro areas is the best way to do it. And not combined metro areas, just metro cores. I could be wrong.
It's absolutely subjective. I composed my lists with very little other than my own experiences and preferences on my mind. Ranking using metros is probably the easiest way to do it.