SharePoint 2010 / 2013 - Create, Add or Promote User Account to Farm Admin Account Rights

As we all know, adding user accounts to the Farm Administrators Group in SharePoint does NOT give those user accounts the same access/rights/security as the Farm Admin Account.

The Farm Admin has additional SQL rights/roles on the databases (config and content), as well as being added to multiple local server groups, providing access to the Sharepoint Powershell snap-in Admin Group.

Octavie has a great post on this. Take a look for more info:
blog.octavie.nl/index.php/2011/11/07/creating-additional-sharepoint-2010-farm-administrators/