everyone's comments seem to be arguing for traffic. The post isn't about traffic, it's about "natural traffic".. SEO puts you closer to the top in search engine results. That brings in natural traffic. The person that clicked your search engine link was looking for something you specifically had on your website. Promoting your link on other websites brings in traffic to people who werent looking for that specific information, but happend to notice your link and clicked for any number of reasons.

Both are great, but natural brings in more consistant traffic and lower bouncerates only offered by SEO.