No difference the preview was just what it was called when it came out because Office 13 wasn't out yet.
I'd definitely go with the 64gb + type cover for 272. The whole point of this OS is that it is the cheapest, best way to have MS Office out and about, and that requires a reasonable keyboard. However, keep in mind that this is Microsoft being as evil as they can, excluding Chrome and itunes and all their other competition and then effectively giving the hardware away. So it's a great deal, but it is a deal with the devil.