Adequate principal preparation and subsequent lifelong learning are of paramount importance in offering the ingredients for coping in multifaceted and highly demanding school environments. This article addresses the following research questions: (1) How do a theoretical and reflective component compare in terms of perceived (a) practical output and (b) professional well-being outcomes in a preparatory programme? (2) How does the component ascribed added value associate with (a) learner and (b) learning contextual factors? (3) Which fine-grained aspects of reflection group functioning are determinative of principals' eventual appraisal in overall terms? and (4) Which guidelines can be formulated on the combination of a theoretical and reflective component in one formally organised professional learning trajectory? This study used a quantitative design. All principals enrolled in a Flemish three-year principal preparatory programme (PP) during school year 2020-2021 were surveyed. Principals who completed the PP the year before were invited to reflect on the programme's dual set-up in hindsight. The article introduces the reader to the PP, research antecedents, and the research design before moving to the data analysis.