An NDA is a useful tool when pitching your idea to prospective investors and even when searching for patent attorney’s for your idea. By state and federal law patent attorney’s would have an obligation to not reveal your idea and it would be bad for business, so an NDA for them would just be double protection. The key difference is that a patent is a more secure form of protection as everyone knows that you have exclusive rights to this idea. While an NDA can only shield the idea from whoever you had sign it. For example if someone signed an NDA and disclosed the idea in a public place to a friend other individual’s overheard they can take that idea since you do not have legal ownership of it. Moreover, if someone else came up with the same idea on their own and filed a patent they now have legal ownership of that idea and the NDA doesn’t not really help you anymore.