A question which is often asked on the Connect Forums is:
"Which is the best Enterprise Vault Outlook Add-in Version?"
That's actually an interesting question. For me the answer lies in the 'big change' that took place in Enterprise Vault 10.0.2. Taken from the release notes we see:
Single Outlook Add-In installer for all supported languages [Ref 13446, 13729]
In Enterprise Vault 10.0.1 and earlier, there was a separate Outlook Add-In installer for each language that the Outlook Add-In supported.
In Enterprise Vault 10.0.2 and later, there is a single installer for all supported languages. The installer kit (Symantec Enterprise Vault Outlook Add-in.msi) is in the folder Symantec Enterprise Vault\Outlook Add-In on the Enterprise Vault distribution media.
The display language that the Outlook Add-In uses is based on the Microsoft Office and Windows language settings. The Outlook Add-In uses the Office language, if it is supported. Otherwise, it uses the Windows language. If the Outlook Add-In does not support either language, it uses English.
It is possible to configure Office to use one language for the user interface and another language for the help. In this case, the Outlook Add-In considers each of these languages separately and, if necessary, uses the Windows language or English.
So for me any version of the Outlook Add-in 10.0.2 or higher is a good one to pick, because it's much simpler in terms of deployment and manageability.