Just look at what it returns for the query "earth"
As opposed to Googleing "earth"
Check out some of their suggested sample searches.
Like the "International Space Station".
I find WloframAlpha much more information at first glance.
WolframAlpha does give you it's source for the information,
But it's limited to what you see on the first page.
Google, on the other hand,
Will give you every bit of data you're looking for,
You just have to know what your looking for.
There are plusses and minuses to both engines.
I'd be interested to see what would happen if you where to combine the two somehow.
WolframAlpha is being bombarded with curious users,
So you may get an error screen.
Just hit refresh and it should work fine.
It's pretty cool,
As far as error screens go.