Hi,
  in this moment I have created an ANSI database but I'm thinking to upgrade that to UNICODE.
I have read the reverse engineering procedure etc etc but I don't know what happens in the future

What Benefits and disadvantages I'll have ??

Now I'm working with delphi 9 (in a few time delphi 10) and EDB 2.03

good question

Which is the more fastest ?
Which Developer Enviroment ( VB6,VS2008 C#.... )  don't can access to Ansi
or Unicode ODBC ?
Database file is more big in unicode mode ?