The other one was just a demo showcasing the hardware of the WiiU and what it could do. That showcase just happened to have a Zelda coat (which they have done since the N64). This was known since minute one, no one should have expected that to be what Zelda U would look like.
Moreover, while I like the realistic style better for Zelda usually, I find the actual style technically far more impressive. Of course, they would have improved the realistic style also, but still, I'm definitely not complaining. This is also a very different case than Wind Waker's anyway. This style is way more refined and detailed.
Also, Wind Waker enjoyed immediate back-lash. And major one at that. The trailer they showed at reveal was even more cartoony than the end product, which they had to tone down because of the bad reception. This Zelda however, or the trailer they showed, has seen almost nothing but praise.
