Newbie : ADO vs DBExpress (D7 + MSSQL 7)


I have D7 Enterprise and MS SQL Server 7.

I would like to know what is the best choice between ADO and DBExpress ?
For information, I already make some tests with D7 Update 1 for msssql DLL.
All work fine.
But ADO seem to be slower than DBExpress.
Is there an article somewhere about ADO vs DBExpress ?

Thank you