I cant tell you much about Audit Vault expect if you are looking for a tool that needs to audit/secure more then Oracle DB´s you cant use it and i dont think they have the scanner that are needed to be PCI DSS 3.1 compliant.
IBM Guardium is a great tool, its one of the "big boys", it has everything you need to get PCI DSS 3.1 compliant concerning the DB part.
PCI DSS 3.1 (3,5,10,11 and helps with 7,8)
it also helps if you have MSSql or even MySql Servers.
i do recommend that you take a look at Imperva SecureSphere to.
+1 for Imperva SecureSphere, especially for latest versions. RDBMS and NoSQL coverage might be bigger than Guardium. Performance both Guardium and SecureSphere agents are equal.