Which metrics are you looking at?
Remember that if you are using something like Visits or Unique Visitors, and you break those down, the total shown in Workspace will be de-duplicated.... this is not the case for Data Warehouse.
Data Warehouse will only export out the individual rows of data based on your column configurations. If you try to add all these rows together you can easily get higher counts.
Without seeing the specifics, this would be my best guess as to what you are seeing and why the values aren't matching.