I've been thinking of Shattering patch as an expansion. I mean, just think of the huge amount of new content. Just guessing I started thinking that the free patch was bigger than the expansion it's meant to introduce. So then I asked, which has more content?
For me, I'd guess that Shattering now vs. Cataclysm week one, Shattering has more content. Sure, a few zones are essentially unchanged; so far I've noticed that Arathi for the Alliance isn't majorly different; mostly some quest progress smoothing and tweaking of the timeline. Iapetes reports that Ashenvale isn't much different for Alliance either. But Teldrassil and Darkshore are quite different, and as I've posted earlier, a whole lot better. Dun Morogh and Loch Modan are much changed, with a major expansion of the troll and dark iron conflicts. Wetlands was fun, but perhaps because the progression was so smooth, it felt insubstantial. Not spending most of my time traveling and lost in marshes really changes the experience.
But what if I had started say, today? For a new player the new zones aren't new at all. They're the current zones. Not old, but not new. For a new player WoW has as much content before 60 as it did at the end of vanilla, less if we count that Zul'Gurub and Naxxramas are gone, but since I'm not counting instances added (Were there any? Don't answer that.), let's ignore the raid changes. My point is that all this new content isn't added content, it's replaced content. So Vanilla vs. Shattering isn't a matter of amount of content, but quality of content. While I inevitably mourn this or that change, I see the new content as giving a much smoother playing experience.
New for old and old for new, how much content was added for you?