SUMMARY OF DIFFERENCES BETWEEN SEO AND PPC?
In summary, the main difference between SEO and PPC are the risks involved.
With SEO, you are trusting the search engine optimiser to achieve good positions. Even experienced professionals sometimes fail to achieve their goals and even when they do, a change to an algorithm can see positions lost in a period of months, weeks or even days.

With PPC the chances of losing positions dramatically are small. You should always be near the top of listings, provided your bids are high enough. However, these guaranteed positions come at a price and with competition increasing day by day, staying at the top can become a big expense.