Provider Summary
Microsoft's OracleClient
TBD
Oracle's ODP.NET
TBD
Core Lab's OraDirect.NET
Core Lab is virtually unknown to me, but that doesn't say anything about their products. As a matter of fact, based on Core Lab's self-evaluation, their provider is better performing than both Microsoft's and Oracle's providers. Of course, I can neither confirm nor deny these allegations, so you'll have to do your own tests.
http://www.crlab.com/oranet