I've lived in both the bay area and NYC, but my answer might be biased since NYC is home. Here are the key benefits over Silicon Valley:
10 years tax free for startups. No income tax, business, corporate, state or local taxes, sales and property taxes, or franchise fees.
- Access to a lot more markets than just tech (finance, advertising, fashion, food)
- Fastest growing ecosystem for startups
- You can have a social life in NYC completely separate from work, and have friends that work in other industries.
- There is no need to have a car in New York.
The biggest downside: You have to be self-motivated to survive in New York. Since you're not constantly surrounded by people doing what you're doing. The bay area has the upper hand in that aspect.