The full mesh configuration provides a direct path between each pair of sites. Fully meshed dedicated networks perform exceptionally well, but the cost can be prohibitively high. The partial mesh requires that some sites connect to other sites through intermediate sites. Therefore, a catastrophic failure can isolate a portion of the network, and a congestion condition at an intermediate point can cause a serious performance problem at the tail end of the network. Whether the configuration is that of a full or a partial mesh, dedicated networks offer real advantages in terms of performance.
Availability is an advantage, as the network and the circuits which comprise it are always on.
Also, the network can easily be monitored to ensure that the level of error performance is maintained at a very high level. There is a downside to dedicated networks, as well. Cost certainly is an issue. Specifically, the cost of a dedicated circuit is sensitive to bandwidth and distance. In addition, dedicated circuits are susceptible to catastrophic failure, which we call backhoe fade in the wired world.