[diegogcouto]

In my experience, we're able to create a lot more engagement using Facebook, but you have to consider that we're a niche startup in Brazil (where CPC seems to be cheaper).

On the other hand, most of the users we got from Facebook were a kind of "freebie hunters". As soon as they saw it would be necessary to pay a monthly fee to use our services (It's an app! Am I really supposed to pay for this?), most of them disappeared.

In the end, as someone has already mentioned here, Facebook seems to be a really good place to advertise free stuff or products that can naturally trigger some emotional response (Look at this lovely products made by this grandma)... and maybe just them.