NDA is a contract, and contract law is an entirely separate field from patent law. How contracts are interpreted is a matter of state law, and interpretations vary from state to state. Our firm practices patent law, which is federal, and so is interpreted uniformly throughout the United States. Another thing NDA gives you a limited level of protection and in many cases it can easily be bypassed, a patent offers you rock-solid, legally binding, enforceable-by-stiff-penalties PROOF of idea ownership.