For synonyms constructed on tables, no changes are required to the synonym to reflect changes in columns on the underlying table. The synonyms adjust automatically when adding or removing columns on the table upon which it is based.

For views, changes are often required to reflect changes in columns on the underlying table.

If you remove columns on the table, then you have to alter your view to remove the columns in the view as well. If you add a column on the table, then you have alter your view to see the new column.

However on the "downside" of synonyms on tables, I have not been able to make them linkable from MS Access which would be great if I could. They just do not show up at all in MS Access. I can link to views from MS Access.