SEO vs. SEM

Since the ability to advertise on search engines became apparent to business owners and webmasters, variations of internet advertising and a combination of online and offline advertising for websites was born. Then the discovery of search engine indexing was exploited, and webmasters worldwide found various ways to trick search engines into ranking their web pages higher up on search engine results pages.
Search engine optimization and search engine marketing is a science. A perfect mixture of user experience and search engine spider experience makes a high ranking website. In the same breath of a perfect mixture, that mixture is very difficult to obtain. So there is much debate in what pays off more, search engine optimization or search engine marketing. I believe that both have their values and are both equally important to creating a successful website. You really use search engine optimization to pretty much index your site properly, monetize your site (again for proper indexing) and to link your site to as much relevant content as you can. When search engine marketing, Google AdWords for example, can be successful only when search engine optimization is done properly. With any ppc campaign you are looking for short term results and long term results, if you are looking to only use sponsored links to drive immediate traffic, then you need to re-evaluate your goals and try to find a purpose for spending the money. A good PPC campaign will bring in immediate sales with long term effect, maybe even repeat business. Let's face it, if you just built your website and nobody knows about it, chances are you are looking or have looked at different ways to get people to your site and SEO was one of your options. Which is great, SEO should be on your mind, but think of it like this, if you don't already have steady traffic coming into your site when you start to perform SEO, SEO is not going to start raking in the gold. You are going to have to market the new website in anticipation of it being useful to people. So when the spiders index your site and there are people worldwide that visit your site daily, it will have a very good result on your first indexing, giving you immediate results.
So again you ask which is better SEO or SEM, here is one reason why SEO and SEM should be thought of as a team, and not opposing teams. One looks out for the other, and without SEO there would be no SEM, and without anyone competing for the first page, there would be no need for SEO.