I had 6 and then upgraded and I would definitely go for the version 7. It's got a lot of stuff that version 6 didn't have.
If you buy 6 and then upgrade, you will have to keep version 6 as long as you have 7 because 7 requires the serial number from 6 in order to work. I'd say just buy the new (not upgrade) and you don't have to deal with that.
