I know exactly where you are coming from: a few years ago I decided I was going to move to either SF or NYC from socal. I interviewed at a bunch of places and spent time socializing in both cities, e.g. going to parties, meeting friends of friends, etc. It was an involved decision that I made carefully.
In the end, NYC was a no-brainer for me. I consistently found the bay area has developed an homogenous culture that even pervaded my non-tech friends' lives. People always asked the dreaded "so, what do you do?" way earlier than they did in NYC. And unlike in NYC, I often felt like I was being judged for my answer. I hated this because I like a strong work-life seperation. In NYC I found there's less of a social "hierarchy" based on profession. At a typical party you can meet an artist, an actor, a doctor, a hedge fund investor, and a marketing executive, and all may kick ass at their jobs. I got exposed to an insane amount of culture in NYC that I didn't see in SF.
Keep in mind that this is written from the perspective of a professional - there are probably large parts of the two cities that culturally overlap. Also, I'm not trying to say SF is a bad city, but it isn't for everyone.
I felt exactly the same way while working in SF, and have noticed a huge difference in terms of culture and diversity here in NYC. That said, if your goal is to build a startup or company, then ideally you should be in whatever location is best for doing that (within certain boundaries, of course).
If you can afford to live in either city and both are valid options for what you do, definitely consider NYC. The startup scene here is blossoming and like rm999 said, the amount of culture and interesting people you run into on a daily basis is amazing.
Living in SF now and have been living in California my whole life, I find the dreaded "so, what do you do?" question something that gets asked during a first time encounter when they've run out of interesting things to talk about. No one likes it, but the best way to answer is to talk about how much you enjoy what you do, not so much the details, otherwise the conversation dies very quickly, no matter your place in the "hierarchy."
In the end, NYC was a no-brainer for me. I consistently found the bay area has developed an homogenous culture that even pervaded my non-tech friends' lives. People always asked the dreaded "so, what do you do?" way earlier than they did in NYC. And unlike in NYC, I often felt like I was being judged for my answer. I hated this because I like a strong work-life seperation. In NYC I found there's less of a social "hierarchy" based on profession. At a typical party you can meet an artist, an actor, a doctor, a hedge fund investor, and a marketing executive, and all may kick ass at their jobs. I got exposed to an insane amount of culture in NYC that I didn't see in SF.
Keep in mind that this is written from the perspective of a professional - there are probably large parts of the two cities that culturally overlap. Also, I'm not trying to say SF is a bad city, but it isn't for everyone.