One often proffered guide for OR model building is that the model should be made as simple as possible subject to meeting its purpose. In healthcare operations management the purpose of an OR model is often to persuade the appropriate stakeholders to modify a system in a way that (hopefully) turns out to be an improvement. Hence the choice of model can be very context-specific, depending very much who needs to be convinced of what. This general issue is examined via a brief description of five different modelling approaches that have been used to support operations management of outpatient clinics. The extent to which the approaches might be 'fit for purpose' in different is discussed.