I had mixed results with a small sample of about 100 paid clicks. Compared to AdSense, Facebook had 2X the percentage of users who signed up for a free account

I had mixed results with a small sample of about 100 paid clicks. Compared to AdSense, Facebook had 2X the percentage of users who signed up for a free account. However, it had only half as many goal conversions, where the goal was simply using a free application. Kind of weird. I probably need to buy some more ads and rerun the campaigns before I make any conclusive judgments though. Costs were similar between the two. If I do PPC in the future, I'll probably do about 30% Facebook, 70% Adsense unless the conversion rates change dramatically.