Rooted in historical linguistics, variationist sociolinguistics is often concerned with diachrony as reflected in synchronic grammars. World Englishes (WEs), which emerge through particular sociohistorical factors (e.g. colonialization, language contact, mass migration, dialect mixing, etc.), provide an ideal window for examining questions that are central to this mission: the inheritance of shared features, ongoing evolutionary mechanisms, and pathways of innovation as dialects interact and settle within new local linguistic ecologies. These varieties thus extend our knowledge base concerning the underlying mechanisms of language variation and change. In so doing, they enable theoretical and empirical advances through application of the comparative method, exposing the interaction between external social forces and internal linguistic ones on linguist forms and functions. In this chapter, I review variationist research that targets multiple varieties, both in the Inner Circle and, where available, the Outer Circle, to outline the gains that are possible by harnessing the synergistic energies of WEs through a variationist lens.