Two separate p2p sharing protocols.
http://en.wikipedia.org/wiki/BitTorrent_(protocol) and Gnutella - Wikipedia, the free encyclopedia which are separate.
Torrent files are usually linked to a website when they are initially hosted. Everyone must download this torrent file before they can start downloading the actual torrent file content from others.
Whereas Gnutella files are simply files that are shared from any gnutella program's share folders.

In simple terms, I guess comparing the two is like comparing two different kinds of public transport, both can reach the same destination but in their own way.

For private sharing on Gnutella network, good if you can get friends together.

For Torrents, there are what's known as Private Torrent sites which have restricted membership. However LW is not an accepted torrent program at any private torrent site I'm aware of.

For more on privacy using torrents, Sleepless & Peerless would be best two to ask here I guess.

For overall privacy on Gnutella network, I guess using proxy connection is one way, however they are often unreliable for connecting p2p through and even after that, finding ones with reliable speeds can be limited.
There are options like Tor. has a small list of options