Should we become an incorporated non-profit or is an unincorporated non-profit with tax exempt status enough for one large event per year?

We put on a yearly community event around the theme of public safety, health and community building. This event gets larger each year and it's becoming difficult to sustain the event on the small donations we manage to get without tax exempt status. We want to be able to solicit larger corporate donations and donations from corporations that only donate to tax exempt. We won't maintain an office or have paid employees. We are in New York and I want to make sure we choose the right option and that we can continue to put on this event every year. We don't have any money to start this and in my research i see that tax exempt status for under $50k is a $275 filing fee. We will have to raise the money to do this so I want to make sure we choose the right root.