The two server approaches have advantages and disadvantages. Nondedicated servers allow for more flexibility, since users can make resources available on their computers as necessary. However, a nondedicated server approach requires that the users are willing to take some administrative responsibility for their computers and it necessitates that they be somewhat network-literate. Backing up the shared data, setting up security, and setting up access rights become more complicated and often become the responsibility of the user, not the administrator. Another drawback is that nondedicated servers often suffer some performance degradation when being used simultaneously as a workstation and as a server.
Dedicated servers have the opposite advantages and disadvantages.
They are easier to administer since all data is in one place. They are faster because they don't have a local user to serve. On the other hand, it is harder to make resources available on an ad hoc basis, since setting up a server is more difficult and time-consuming. If a dedicated server fails, all users are forced to stop working because all resources are centralized. Your choice of dedicated or non-dedicated operation will depend on the work your network is doing.