Agent service confusion

I am running into the use case which needs clarification on

iPlanetAMAgentService vs sunIdentityAgentService

The service schema are the same hit

(1) I understand BasicAgent's CreationTemplates handles agent creation
   via standard AM UMS object

(2) iPlanetAMAgentService and sunIdentityAgentService seems to have the
   same schema service attributes
   however,the attribute      
   "description", "sunIdentityServerDeviceKeyValue"
"RequiredValueValidator"
   does not show from amConsole

(3) In addition what is the usage of the two services
   iPlanetAMAgentService vs sunIdentityAgentService