There are lots of difference in Social Bookmarking (SB) and Social Media Marketing (SMM) although both generate traffic to site but SMM is much better in order to get targated traffic to site.
On the Other hand some social bookmarking site give you do follow back links along with traffic.
Social bookmarking is designed for users reference, it is a place where you can add, edit or save web documents.
On the other hand, social media marketing is a way to increase business' online presence as well as reaching its target audience.
Both are sharing information of a website but way submission is different, In social bookmarkings only URL submission and in Social media we can submit images,videos etc... also.
Social bookmarking is the method in which url submission is done and backlinks are created which will increase the ranking of the website on search engines. Whereas social media promotion is done to promote your website on social media platform to get maximum traffic.