Abstract Context-sensitive graph grammars are natural formalisms for the generation and parsing of visual programming languages. Being intuitive, rigorous, and expressive tools, they have been frequently employed in a wide range of research fields. Nevertheless, the expressive powers of the existing context-sensitive formalisms have not been investigated yet. To this end, this paper is dedicated to the comparison of expressive powers of the two prevalent graph grammar formalisms, Reserved Graph Grammar (RGG) and Edge-based Graph Grammar (EGG). By introducing a special variant of RGG as an intermediary, the relation between them concerning the expressive power is revealed that the set of graph languages of EGG is a proper subset of that of RGG. Moreover, bidirectional transformations between EGG and the variant of RGG are accordingly established, allowing them to take the advantages of each other in applications.