Is it just that nvarchar
supports multibyte characters? If that is the case, is there really any point, other than storage concerns, to using varchars
My two cents
Indexes can fail when not using the correct datatypes:
In SQL Server: When you have an index over a VARCHAR column and present it a Unicode String, SQL Server does not make use of the index. The same thing happens when you present a BigInt to a indexed-column containing SmallInt. Even if the BigInt is small enough to be a SmallInt, SQL Server is not able to use the index. The other way around you do not have this problem (when providing SmallInt or Ansi-Code to an indexed BigInt ot NVARCHAR column).
Datatypes can vary between different DBMS's (DataBase Management System):
Know that every database has slightly different datatypes and VARCHAR does not means the same everywhere. While SQL Server has VARCHAR and NVARCHAR, an Apache/Derby database has only VARCHAR and there VARCHAR is in Unicode.