vCenter Log on as a Service Concerns

Question

I was installing VMWare vCenter Server 6.0 on Windows Server 2012 R2 when I came across vCenter Server Service Account feature. I can use a local system account or specify a service account on my domain. After doing some googling, I have found that a service account allows processes to be run on a machine as a user even if there isn't a user logged in. However, I don't quite understand why I would want to do this or how I could benefit. If I were to do this, would I want to create a new account to use exclusively as the service account? Is it recommended that the account have domain or local admin?