Here are the main advantages of one and another:
1. SEO - inbound links greatly influence page ranking, also relies in large part on title tags, headers, image title, bold text and proper keyword usage, aims to make a site easy to read for search engine spiders, places high priority on content quality and site structure.
2. SMO - proper implementation will benefit SEO efforts as well, not so much importance placed on coding and tags, relies in large part on visually attractive and striking elements, places a lot of importance on titles and headlines,
aims to make a site easy to read for humans, quality content is essential for maintaining reader interest, relies on visual impact as well.