With the rise of the social media phenomenon, not more than a decade or so ago, one can wonder today, what is the best venue to use for your online marketing.
SEO Marketing
We don't have to worry that Google search engine will stop being used any time soon, it's embedded in too many places, and the database itself is too relevant to become obsolete. I use Google as the example search engine, but in many respects the SEO is performed similarly for other search engines, like Yahoo!, Bing or even smaller niche ones. The main distinctive request is that the crawler of the respective search engine be allowed to crawl your website, to gather information about it and the future changes.
So someone will never get it wrong optimizing for search engines marketing.
Search engine optimization aims to offer proper information to a crawler, an automated program which from time to time parses your website pages. Based on what it finds and the search algorithm, you get a rank when someone searches for certain terms using Google search engine.
When you are optimized for search engines, you have a chance to rank higher and more people will see your link and potentially click on it.
The less optimized your content is, the higher the chances to rank lower and your content to be hard to find using a search engine.
Sometimes SEO is made by certain tools or plugins, without you being aware. You just write your content and leave the details to these plugins (often on Wordpress) or to people who are specialized in this job.
Social Media Marketing
I know I've given you a nice talk about SEO above, but do you still need a website or even a blog or can social media successfully replace all that?
I know people who don't search on Google. They search on Facebook. Does that mean that if you're not on Facebook you don't exist? They surely won't find you if you have a website, but not a Facebook page.
Judging by the sheer number of users, one can think if you don't have an account on Facebook (or lately and especially for the new generation, on Instagram, also a Facebook Inc. website), you don't really exist. If that is true, it means I don't exist, at least in the social media prime world, because I deleted my personal Facebook account and I never had an Instagram account.
However, even for those addicted to Facebook, this is the way marketing works:
They learn about a product or service via a friend's post, and if they are interested to know more other than what they've read from the friend, they expect a link that should go to a place outside Facebook, whether it's a blog or an e-commerce or a membership or a simple presentation website. That still looks much more professional than a free Facebook page which you don't own.
In Conclusion
The quality of your SEO (which can be done automatically or by a specialist) influences the quantity of organic traffic you receive to your website.
Word of mouth from social media partially converts to organic traffic for your website or blog.
While search engine marketing (SEM) has an algorithm as a middleman, social media marketing is facilitated by the word of mouth we can only find in a social environment.
That's why the two marketing methods are simply based on two distinct paradigms, which are complementary. You can't truly say one is better than the other because they work in different ways. You can however be better at using one marketing method than the other, or one works better for you than the other in a certain context.
If you want more eyes on your website or content in general, simply optimize your content for SEM and drive traffic to it from social media too.
The worse mistake you can make is to be self-sufficient, and do neither of them. After a while your base of users/members/readers erodes, and you will have done nothing to replace it or increase it.