If you need a shopping module for Joomla, Virtue Mart might be of a help. Now it also depends on your needs, because if you want to create a professional online shop, with a lot of functionality included, there are other solutions. However, if you only want a basic cart you can implement Virtue Mart in Joomla.
So , I don't believe there is a general "best module", the best module for you is the one that suits your needs the best.
Hope this helped