I would like to have an experts advise on social media marketing, why this is the best then other marketing?

It is not so much that social media marketing is the best, it's more about how effective and efficient it is. Social Media Marketing, unlike traditional marketing, is free for the most part. What you get out of social media marketing is the ability to target the market you need to target without having to spend money on doing so. There is no tangible marketing that needs to occur, which means no magazine advertisements, no television advertisements, no billboards, etc. You have full creative control over what happens in your online marketing. You get to create a style guide for your marketing campaigns, implement call-to-action methods that allow your target market to access information at their convenience, and so on. 

What I like about social media marketing is that you get so many ways to advertise and market your products and/or services without having to go through a middle man and worry about PPC and CPC. The only real aspects of social media marketing that you need to take into consideration is SEO. What this means is focusing on keywords that allow you to move up in rank on search engines, specifically Google. This can also be done organically via SEM. The more people search for your specific company/brand, the more exposure you get...which, in turn, means you move up in your ranking on Google.

I honestly prefer social media marketing over other methods of marketing simply because of the reasons I mentioned above. Although I do implement all marketing techniques, I definitely do favor Social Media Marketing.