I have both GPA and GoCollect. They each of their advantages and disadvantages. To me, the biggest weakness of GPA is the lack of Comiclink sales. Many good books are sold in Comiclink auctions at good prices that never make GPA. For GoCollect, they are very inconsistent posting sales. For example, say 10 books sell in a ComicLink auction, go collect might post 3 or 4 sales within a few days while the others might never appear. The same holds true for Ebay and Heritage sales in GoCollect. I use them both regularly as I want as much informaiton as possible when purchasing a book.