Winstation: The winstation workstations setup requires constant network communication with the server. Each winstation configured has a dedicated process on the server called ops.exe which is responsible for facilitating the communication between the workstation and the database.
SarOps: This stands for Stand-Alone Resiliency. As the name suggests it has the ability to stand alone in the event of the server or network failure. There is a process on the server called Possrv.exe which manages multiple workstations.
Winstation: As mentioned above these workstations require constant communication with the server. If at any point the server or network fails then the pos system will be unusable. All workstations will revert to the default "Contrast up | Contrast Down" display and will show a communication error in a grey box in the middle of the display.
SarOps: If the server or network fails and you have a SarOps configuration then the workstations will advise you of the communications failure and enter offline mode. In offline mode you can process orders and take payments as usual. You will obviously not be able to perform tasks which require communication across the network but you can access the menu, print local orders and take payments. Once the server or network has been restored you can bring the workstations back online and it will upload the sales to the main database.
In theory the operations of Winstation's is much simpler and easier to configure but SarOps offers more stability.