In Donedesk, use tags for most contexts. Specifically, use tags for all personal contexts; use workspaces for shared contexts.
Example: A shared Errands list lets anyone in the family do the shopping if they happen to be at the store. Use a workspace for it (“Family Errrands”) and invite other participants. All tasks that are errands get assigned to this workspace.
Example: A team meeting context is ideal if it is shared, so everyone can see and add agenda items. Use a workspace for it (“+StaffMtg”) and invite other participants. Shared agenda items get assigned to this workspace.
Example: It’s handy to keep a list of Calls. If you find yourself waiting in the doctor’s office, you can pick up the phone and make good use of the time. Since this is not shared, you use a tag for it (“Calls”).