I was going through my recent newsletters and blogs today when I came across an article about the battle between the two. Personally, I do not think there is a debate and it is almost irrelevant to compare the two. It is like comparing apples and oranges. I mean, truthfully in the end one can aid the other, and depending on the funding that your organization has for marketing and advertising purposes, you should be doing both.
Granted, there are some points that you can use to determine which option that you should spend more time on when first starting out and what not. Generally though, I find there is no good reason to use one without the other.
An example of how to use SEO and PPC together is by using PPC in order to ramp up your SEO traffic though brand awareness. So, what do i mean by that and what does that mean in general? I have heard from customers and other contacts' customers using both PPC and SEO say they used the site because they saw them in both sponsored and "regular" (obviously organic in our eyes) results. Basically, this is just adding validity to your company. E.G. you are ranked highly for "home loans" in both sponsored and organic listings in the SERP results, people think of your brand as "The Home Loan Guys." Yes, this is a very casual approach no doubt, but still very true in many ways.
Finally, i've also witnessed high PPC listings as a way to help you start boosting and ramping up your SEO efforts through both link building, page views, etc. It is a trial and error process that does work for some and not for others, but there is no sense in putting no effort into it, you never know what you are missing out on until you give it a shot.