What is the difference between EmptyStringType and EmptyAnsiStringType?

I am looking for a user type that will not only map database NULLs to empty strings and vice-versa, but to trim trailing blanks from CHAR() column values. Is this what EmptyAnsiStringType is for?

I still can't fathom why my boss insists on using CHAR() instead of VARCHAR(), but I have to live with it ... something to do with the inevitability (?) of trailing blank crap getting into VARCHAR columns, and then values with and without trailing blanks not matching in SQL statements ...