Client satisfaction is considered today as one of the main concern to be ensured by enterprises, especially in e-business, where client position is central. With the spread of concurrency and the increase of functionally equivalent services, QoS became an important criterion, which is closely related to client satisfaction. In this context, we propose an approach to determine the satisfaction degree corresponding to the QoS of service-based applications, with regard to client's QoS expectations. Our approach is based on a preferences model, which is built only on the basis of client provided information. This preferences model is also based on the 2-additive Choquet operator that supports preferential dependencies. We present a study that compares the results obtained from our preferences model with those of related work, and shows that our approach provides more accurate results in the way that it represents more precisely client satisfaction.