We recommend that the task servers be at least comparable to workstations used in production, if not stronger, especially if you are planning on running multiple sessions of Revit and or multiple logins (not typically recommended due to permission issues).
When referring to the Revit System Requirements.
Do not go with anything lower than the Value, but Performance is recommended, or value with double the ram if you have large models with multiple links.
If you choose to use virtualization, be aware that graphic intense tasks will not perform as well without a physical graphics card. Refer to the Virtualization section below.