I have no idea why Academy chose to issue two kits representing the same ship on such similar scales. I've never had either of them in my hands, but I have the impression that the older one wasn't bad - certainly better in many respects than lots of sailing ship kits that have been released since.
Some time back we had an interesting discussion of the new kit here in the Forum: /forums/1066618/ShowPost.aspx . The discussion started by establishing that the new kit is indeed something other than a reissue of the old one. Another member linked us to some photos of both of them. I was struck by the similarity of the newer kit to the old Imai one - which I've long regarded as the best representation of the Cutty Sark in kit form.
Not having actually seen either kit "in the flesh," the comments I made in that earlier thread are the best I can offer.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.