Not sure what the AIGA would have for marketing, it is a graphic design based organization (to the best of my knowledge, though I haven't really done much more than read a book or two of theirs, etc.).

So I think that leaves SMPS as your best choice.

In my experience (not in NYC) SMPS is a sound organization and attracts marketing professionals from a wide variety of architecture and engineering firms. Here in our area, they tend to put on good programs and I've learned a lot about the marketing of design services from participating over the years.

However, in our chapter the vast majority of participants tend to be Marketing Managers and Marketing Coordinators. A few firm principals also attend. Consequently, opportunities for learning through networking tend to be limited since nobody there wants to share any really usefull information with a competitor -- which is totally understandable.