This study contributes to the research on external Enterprise Resource Planning (ERP) service providers in the German-speaking countries and identifies potentials for differentiation of their service offering. Specifically, it focuses on the Swiss mechanical and electrical engineering industry (MEM Industry) and analyzes the added value of external service providers for the ERP implementation as well as subsequent operations and maintenance of the ERP system. The results add to the existing research on critical success factors, which have been studied mainly in the context of ERP implementation success within the ERP adopting companies. Based on data from a survey with 59 companies, this paper allows assessing the contributions of ERP service providers with respect to the major critical success factors of an ERP implementation. Companies using an ERP solution from one of the main software vendors (e.g., SAP) perceive external service providers more beneficial than companies that use more customized and, therefore, less comprehensive systems. According to the participants of this study, the greatest benefit of external ERP service providers is the quality improvement during the implementation phase as well as the increased stability of the IT infrastructure. An increased quality improvement through enhanced data consistency leads to a differentiation of service offerings. Thus, ERP systems with the function of an integration hub enable sustainable quality improvement and service differentiation.