Handling multiple languages specific character within a single database is difficult to manage. It is also difficult to translate language specific data or special character in a correct format without using any code page (template). Now on days database use to support worldwide clients (local and international) and it’s advisable always to use Unicode data types instead non- Unicode data types.
Unicode is a standard used by sql server for mapping code points to character. All the special characters of all languages are included in Unicode design so that using single code pages can handle different sets of characters.
Unicode character is depends on Sql or windows collation, collation is based on language used for table or database. Unicode character stores double byte in Sql server whereas non Unicode data takes only single byte per character.
If you are managing international databases then it is good to use Unicode data types i.e nchar, nvarchar and nvarchar(max) data types instead of using non-Unicode i.e char, varchar and text.
If your application has developed on international database then make sure, it is using Unicode variable instead of non Unicode. There won’t be any performance issue as system does not have to perform character translation.
Storage and Performance Effects of Unicode : http://msdn.microsoft.com/en-us/library/ms189617.aspx