1) A superagent is a normal agent with a number of additional abilities: it can host a repository, and it can send messages to other agents on the same subnet.
An agent handler is a much more powerful entity which can handle full agent communications: so it can receive properties and events from machines, and send policies and tasks.
2) I'm not sure I understand the question - there are not really any benefits as such: instead, if you want to use certain features in ePO, you have to register a server to enable that. So if you want to do rollup reporting, you need to register an ePO server, and so on.
I believe this will clear your mind a little bit more.
1.Registered LDAP (Lightweight Directory Access Protocol) server to use Policy Assignment Rules, to enable dynamically assigned permission sets, and to enable Active Directory
2.Register additional McAfee ePO servers for use with your main McAfee ePO server to collect or