As NDA is a confidentiality agreement between two parties but information is still disclosed to a second party and does not guarantee complete protection. Whereas a patent is a document filed with the government and not another entity who has business interests that might involve using your original idea and breaching the contract. In any case, patent law is useful in cases where you can invest and develop your product without the involvement of a third party or their resources to harvest the benefits of the invention. If the invention does not require huge capital investment to develop and harvest it further, patent law is a good option. In most cases, any technological invention requires the backup of high capital investment, professional services and resources that are not possible to obtain without signing an NDA agreement with a company.