xbox 360 premium and xbox 360

What is the difference between an xbox 360 premium and xbox 360 arcade? I am going to get an xbox 360 arcade included with some furniture from roomstogo and I'm wondering what the difference between that and an xbox 360 premium is. I heard that the only thing was the hard drive. If that is the case then could I just buy a hard drive and it would be the same thing as a premium? And also if I did that, could I use xbox LIVE?

[crait]

Yeah, buying a hard drive would allow you to connect to Live if you had a subscription, too. It would be pretty much the same, but Microsoft markets it like they are giving you a good deal on the XBox buy including the hard drive. You should be able to find a hard drive cheap.

You probably very clever? or cunning?