I guess I shouldn't really complain about Boston - like you say, it's got a better scene than most places. It's just that the jazz we have here isn't so much to my taste and the clubs aren't either. The bigger jazz venues here are catering towards baby boomers (and older folks) who want a nice date night with their spouse with fairly safe music - which means it costs a lot, people are not friendly, the crowd is older, and the music often bores me. It's like a very slightly hipper version of going to the symphony. (I have nothing against classical music but the BSO is insufferable...) The smaller venues are often run by people who don't really care about making money (independently wealthy or whatever) who run their venues like a club for them and their friends, and the owners' band and their friends' bands get regular weekly slots... and they don't bother to promote the occasional really good out of town band coming through.
I will say the Boston ICA has some good stuff and they've got a really nice venue for live music, but they only have jazz concerts a few times a year, and a handful of contemporary classical shows.
Whereas in New York I meet lots of people of all ages who are really excited about the music and excited to talk to other music fans, you can find lots of great shows for under $20 (Colin Stetson is playing tomorrow for $10 in Brooklyn, for heaven's sake! And with an opener I really like, no less...), and of course the variety, quality and quantity of music is head and shoulders above what we've got here... and it's like pulling teeth to get even musicians who live in NYC to come play up in Boston. A friend of mine keeps trying to get me to take up the mantle of booker/promoter here in Cambridge because he has such a hard time getting gigs up here for the musicians he reps in NYC...
Trying to compare ANY city in the US to NYC regarding jazz/improv/avant garde music (or any creative activity for that matter) is probably going to be seriously slanted.
Despite Boston's good points the more adventurous types have always struggled to survive.These people struggle in NY as well due to the tremendous expense of survival there.
NY just has a lot more people engaged in this sort of thing, I've always loved this about NY.
I will say that even today Boston is amazing compared to where I've been living the last 2 years or Seoul(where I spent a lot of time the previous 2 years) or even Prague (where i lived before that).The Czech people had a wonderful openness to creative work however. Even the general public, as opposed to a "specialist audience" could enjoy something totally experimental.I've had great times at the jazz fests in Prague but it has a very limited live music club scene.
EDIT:Anyway NY is unique...