It's a tossup.
I like the tagging and cataloguing capabilities of Library Thing. But my library is heavy on the reference/craft books and books I haven't gotten around to reading yet. Books I read and loved were likely passed on to friends who simply must read it, too. Books I read and didn't love were traded in at an used bookstore or donated. What about the read borrowed books?
Goodreads lets me shelve books by status (read, currently reading, to read). I can stop using my amazon wishlist to remind me of the books I want to read.
Where does one find the time to catalog all one's books? I finally got around to culling our cookbook collection and adding them to Library Thing. However, only about 30-40% of our home book collection has been added to LT.
For Goodreads, I will only add books as I read them, or to maintain a list of books I would like to read someday.
Mark's Netflix movie ratings (1048 movies rated!)