The aim of this article is to contribute to the scholarly debate on differentiation processes in higher education, particularly in binary systems. The article builds on recent developments in institutional theory and organizational ecology regarding the nature of "organizational forms," as well as on the mechanisms through which these forms impact on characteristics of individual higher education institutions, and highlight the role of isomorphic pressures and competitive differentiation. The approach emphasizes the relevance of segregation and blending processes between types of institution. An application to the relationship between the two main types in Swiss higher education confirms that these forces largely determine the dynamics of the populations, and that a distinction emerges between core features -- which make the distinction between populations -- and features for which individual strategies and local conditions are more relevant.