I think that’s a REALLY good question elgoog.
I am going to measure “good” by the only stat that ultimately matters – The Greenback!
Each search engine has a different overall demographic of users, so the comparisons I am about to make are between visitors who have clicked an organic listing compared to visitors who have clicked PPC listings.
PPC Visitor – Converts Better.
Organic Visitor – Spends more.
So as a basic overview if you are looking to gain visitors via organic search you will generally be better off going on a revenue share style deal whereas you’ll be better off going for a CPA style deal with PPC.
The above is a HUGE statement and is based on over a million players I have seen via these routes and holds true because of it.
Your mileage may vary of course