I guess the DLCs kinda bring home how special an existence New Vegas is. A place that still has a part of the Old World civilisation, but also a part of the wasteland life.
New Vegas really is a glowing point in the Wasteland. And a big sandstorm decides to hit it in the form of the three-way war between NCR, Caesar's Legion and Mr. House.
Though I guess FO3's setting is symbolic too. Sure, the BoS and the Enclave are vying for supremacy (Good Guy in Power Armour vs Bad Guy in Power Armour), but in the end, it's still the super mutants who control the symbols of power and history in Washington.
The great difference I feel though: You're not thrown into the power struggle, you are basically the cause of it escalating (or well, turning into a battle in DC). Without you, James would be stuck in a simulation and the purifier would stay a lost project for quite a few more years, if not forever.
Now, I wonder what sort of feeling Boston will have. Is it a 'beacon of prosperity' like Vegas? It doesn't seem to be an almost fully lost cause like DC (let's face it, besides the purifier, that place is practically dead).
I'm guessing that it'll feel like New Vegas though, a bit. I'm expecting a copy of the "great clash between major powers, with an unexpected third party [androids]". It's not a beacon of prosperity though, just a sort-of working civilisation. Still, it certainly doesn't look hopeless, what with all the airships.