An SAS 70 data center will have undergone a process to assess its security controls against a set of controls mutually agreed upon by the auditor and the data center.
So the choice depends on whether availability or security is the key attribute in a hosting provider. Most organizations say both, and they are probably right. But if it has to be one or the other, a SAS 70 data center focuses on security controls, and a Tier III is concerned with ensuring availability.
This was first published in August 2008