1) When New Yorkers in Washington ask me where to go to get good deli food, my answer is, inevitably, "New York." Actually, the deli counter at Wegman's in Fairfax isn't bad. But only in New York can you get great pickles. I like half sours, but full sours are the pickles of the gods.
2) I did not, alas, have time to stop on the Lower East Side on the way back and pick up a bialy or twelve and/or an onion pletzel. But you can't get either down here. (You can sometimes get things that call themselves bialys, but not ones worth eating. Trust me on this - my mother's family is from Tykocin, just down the road from Bialystok.)
3) No buskers inside
the D.C. Metro system.
New York has music.
In particular, coming back to the hotel on Saturday night, there was a guy playing a kora on the platform. And on the way back to Penn Station, a mariachi band was playing on the A train. All three of them, including the bass player, moved down the car (and from one car to another - a major taboo in the eyes of the Washington Metropolitan Transit Authority), which reminded me of the scene in Take the Money and Run in which Woody Allen plays the cello in a marching band.
4) New York has better pizza.
5) New York has a theatre district. Washington has theatres, but they are more scattered about. What that means is that Washingtonians have to do more planning.
6) Sadly, the tourist herds in both cities move just as annoying slowly.
I meant to write something here about walking around Brooklyn, but I don't have anything in D.C. to really contrast it with. Maybe I can find some similarity between the way that the monuments just mesh into the residential part of the Hill and the way you cross the street from Borough Hall in Brooklyn and you're right into a pleasant residential neighborhood. I think I'm trying to get at a broader statement about the Northeast since what I like about Boston (and Philiadelphia) is how people still live in the city. I'll have to ponder that more. At any rate, I was surprised by how much I liked the neighborhood around the hotel which had yuppie amenities (e.g. a Trader Joe's) and businesses that meet real needs (an actual hardware store!). I wish I'd had more time to browse the used bookstore on Atlantic or to shop at Sahadi's (a Middle Eastern grocery supplier).