Difference between 'Home sharing' and 'Network sharing'
While both options offer the possibility of streaming the content of up to five iTunes libraries through a home network, it's only through Home Sharing when you are able to actually import the content into your own iTunes Library. 

Even more, when you use a computer on your Home Sharing network to download an item from the iTunes Store, you can have the item download automatically to other computers on your Home Sharing network.

Other big difference is that Home Sharing lets you stream content from your iTunes library into your iPhone, iPad, iPod touch, and Apple TV (2nd and 3rd generation), whilst Network sharing don't.