SharePoint Workspace 2010 (No More Groove) provides much more features like taking SharePoint Site content Offline. The content(documents, lists) can be edited offline and synced once connected in Network/SharePoint server.
Shared Folder is just like a open space where documents or files can be stored. It can't be compared with SharePoint Workspace.
If you want to keep single copy and all your devices are always connected, then "Shared Folder" may fit.