Networks-on-Chip are emerging as a widely accepted alternative for the traditional bus architectures. However, their applicability by the system designers is far away from being intuitive due to their lack of predictability. This communication predictability can be obtained statically or dynamically. A dynamic allocation is more suitable for flexible multiprocessor systems and requires the implementation of a Quality-of-Service (QoS) mechanism. This paper explores the main QoS schemes suitable for such systems: connection-oriented and connectionless. The simulation results show that the connectionless scheme provides a better predictability in terms of message latency with an acceptable buffer requirement. This work provides the designer with valuable guidelines to choose a priori the QoS parameters such that they can be confident on the predicted results.