Trying to clearly distinguish what the roles that Farm Administrators, Site Collection Administrators and also Site Collection Owners each have. Moreover what roles can't site collection administrators do that server farm administrators can in a SharePoint Server 2010 server farm?
Simple answer of this question is: Farm Administrator is the father and Site Collection administrators the kids.
Farm Administrator have full control on SharePoint farm; can create services applications, Web Application, manage quota, deploy solutions, configure the farm level settings, run PowerShell scripts etc.
While site collection administrators, only king of their site collections, cannot access the other site collections or farm level settings, cannot run PowerShell in farm, cannot change any farm level configurations.
In other words they can make changes to their own site collections like add users, create lists and libraries, manage site collection features etc.
Site owners are the same as site collections administrators.