Domains and W/G

[Nestor]

My class has had a 'workgroup' arrangement for our network since time out of mind. We recently began transitioning over to a domain, while I went off to intern for six weeks.
When I came back, everyone was on the domain, except myself. Now, before I connect to the domain, I asked my Admin (who is really just an admin in training) to 'sell' me on why I should switch to the domain, and he didn't have any valid answers. So my question is this: What's the difference?

I figured that since this isn't a problem, more of an info request, it should go here... however if I'm wrong, shoot me in the foot.