I believe small sites are performing better with paid per clicks (ppc).
Larger sites with lots of traffic perform better with cost per thousand impressions (cpm).
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You just place the AdSense on your site and you will get paid both way for ppc (pay per click) and cpm (cost per thousand impressions).
*With AdSense you won't earn much for cpm, very lwo cpm rates. But using the ppc, you will make good revenue.