If OLE DB driver is available it should be used ahead of an ODBC connection.The use of OLE DB negates the need for setting up an ODBC connection. OLE DB simply requires one setup step within QlikView.
ODBC is Open Data Base Connectivity, which is a connection method to data sources.It requires that you set up a data source ( DSN) using an SQL driver or other driver if connecting to other database types. Most database systems support ODBC.So it is user friendly
But OLEDB is the successor to ODBC, a set of software components that allow a "frontend" such as GUI based on VB, C++, Access or whatever to connect with a back endsuch as SQL Server, Oracle, DB2, mySQL etc. OLEDB components offer much better performance than the older ODBC.