Using Domain Login over Workgroup

I am the net admin for my company and I am striking for a domain login and the desire to get away from workgroup logins on client machines (setup before I got here). We have 3 servers: PDC/FILE SERVER, MAIL/EXCHANGE SERVER, and a PROXY SERVER all on the same domain. The PDC is a print server, massive file server, shared program server, and a list of other things. I I could list countless needs to have users login to the domain (login scripts, group policies) but I suppose the biggest fear islack of control and privacy on client machines. Please help me with some ground breaking and major advantages to going to the domain login.