These debugging methods are designed to be used in cooperation with one another. They complement each other at different points in the development process. Where debugging using PL/pgSQL Debugger is highly effective while editing an existing (hopefully well written) function, other forms of debugging may be better suited to the quality assurance or automated data processing applications.
Because PL/pgSQL Debugger is meant to be a visual tool to work within
pgAdmin3, it is possible that the developer may want to forego the visual debugger in the interest of some other feature.