SEO vs. PPC - What Are the Differences?

The question comes up often regarding the differences between search engine optimization (SEO) and pay-per-click (PPC) marketing and which one to use. The answer depends on your specific business objectives and your budget.

Search Engine Optimization (SEO)

Search engine optimization will absolutely provide the lowest-cost traffic to your site but results generally take months to show up and SEO is subject the whims of seach engine algorithm changes.

 Can be thought of an "infrastructure" investment for your site
 Involves a one-time fee and minimal monthly outlay
 Time-consuming to implement, can mean recoding entire site
 Can take months for results to kick in
 No guarantees for a specific ranking
 Targets a relatively low number of high-trafficked keyword phrases
 Has the highest conversion rate and best ROI of any online marketing method
 Highly ranked sites are perceived as being more credible
 Over the long-term is much cheaper than pay-per-click
 Produces long-lasting results - good optimization can last for a year or more

Pay-Per-Click (PPC)

A pay-per-click campaign is the fastest way to drive traffic to your site and is often used to to get traffic while the results of your SEO efforts kick in. The downside of PPC marketing is that you can burn through a lot of cash in a hurry if you don't know what you are doing.

 Is a regular, recurring expense. Traffic stops when you stop paying.
 You can get visitor traffic in as little as an hour after setup
 Solution for exposure on competitive search terms where you can't get a top ranking
 Good solution for "problem" sites that use Flash or dynamic content
 Great for testing new product ideas or the effectiveness of ads quickly
 Goal it to target a large number of low-bid-cost (niche) keywords
 Perfect interim measure until your SEO results show up in the search engines
 Excellent for seasonal sales or other time-dependent promotions
 Easy to measure and track performance and effectiveness
 Very time-intensive to monitor in-house

Source: http://www.bluemoosedesign.com/article-seo-ppc.htm