Debate as much as you want regarding organic search engine optimization or SEO versus paid advertising or PPC and you will find out it is a hot topic with people fighting on both sides of the fence that one is better than the other. A third option we see all too much is to be completely lazy and do nothing as you've vested so much money that you expect that money to also be heard by the search engines that you didn't even pay because your site is just "that great". The question comes down to which one will work best for your brand, your time frame, target market, what your budget is, how patient you are, and whether you have truly great content. We've re-written this several times and are going to lay the pros and cons to each.
When it comes to the search engines you need to think like a runner and not a sprinter. No matter what solution for performing search engine optimization is something your business does. If you want to fail then "do nothing" as that will get you the results you want – nothing. If you have a new site and want that quick adrenaline rush does PPC in conjunction with organic. If you are patient, not in a rush (3-4 months) do organic solely.
As with any marketing for your business you need to determine what is best for your business and brand. You need to do what is best for your company which will not be the same as everyone else.