Directory listing can offer a different type of traffic than social bookmarking, both provide good quality traffic, but I personally think you can go a lot more viral with social bookmarking, as more people will be able to share your link, as with directory submissions you link stays in one spot and does not have a viral nature.
Hi, The social bookmarking sites can be the useful tools for having an improvement of your SEO marketing strategy. With registering on the popular social bookmarking sites you establish more your online presence by providing to the relevant people seeking for more information.