"NYC has a lot of developers, more than the valley" - do you have a source for that? Seems highly unlikely. My quick googling suggests silicon valley has 2x-5x more engineers than NYC.
A summary glance indicates that the Valley and SF may be roughly on par with NYC but that the Bay Area has more than NYC, I stand corrected - though there seems to be scant hard data as it's difficult to define exactly what a developer is ...
NYC was not historically focused on engineering or tech. Media, advertising, and of course - finance, banking, and investment banking.
Pure engineering or software work? Not very much.