Because BDE is generic interface to RDBMS, it can't give to programmer all abilities, that You can find in specific RDBMS API, such as OCI8. OCI  (Oracle Call Interface) is API to Oracle8 server. Also, because BDE is generic, it make a lot of works and data conversions on the path from OCI8 to VCL and backward, it takes a great overhead. NCOCI8 uses directly OCI8. There is no overhead of BDE & SQLLink. As shows my benchmarks, application, that use NCOCI8 is 3 - 6 times faster, than application, that work with Oracle using BDE. For deploying your applications, that using Oracle8 SQLLink, You must have a SQLLink deployment license. In NCOCI8 case You can save this money.