Answer
Ciudadanos naturales are granted status on constitutional grounds related to birth and Uruguayan descent. Ciudadanos legales are foreigners who acquire ciudadanía legal after a prescribed period of habitual residence and fulfillment of requirements. They are not simply different names for the same route to citizenship.
A legal citizen enjoys a broad range of civil and political rights, but differences may apply to certain offices, the transmission of status to children, and documentation. A credencial cívica for a legal citizen is not issued immediately, but after the period set by the procedure.
When making plans concerning family, a passport, or public office, check the specific right rather than relying on the general statement that "rights are completely the same." The key documents are the Constitution, the carta de ciudadanía, and current guidance from the Corte Electoral and DNIC.