OLEDB Vs ODBC Which is the best driver for connecting Oracle from SQL Server using Linked Server or DTS packages

What is difference between OLEDB and ODBC: OLE DB is not intended to be a replacement for ODBC. ODBC, or Open Database Connectivity, is a well-established standard for connecting to relational databases. It has been extended a little bit to connect to Excel spreadsheets and text files, but for the most part; it is designed for connecting to relational databases. However, OLE DB can access relational databases as well as nonrelational databases. Typically, your data is stored all over the corporation. There is data in your mail servers, directory services, spreadsheets, and text files. OLE DB allows SQL Server to link to these nonrelational database systems. For instance, if you want to query, through SQL Server, the Active Directory on the domain controller, you couldn't do this with ODBC, because it's not a relational database. However, you could use an OLE DB provider to accomplish that.OLEDB is much faster than ODBC so it is suggested to use OLEDB in your connections.

Comparison of response time of drivers from SQL Server to Oracle(in Seconds)
From the above data we can understand that Oracle provider for OLE DB is the best driver! But still even after selecting this driver we will get unknown errors in Linked Servers...