There are literally hundreds of pay per click Adsense alternatives and do not have the resources to evaluate each of them. The problem that all of them have is that they do not have the massive reach of Google Adsense. Those programs have to work with a limited amount of advertisers. This leads to a few problems, it does not actually have to mean that you will make less per click than with Google Adsense but it - most of the time - means that the ads displayed will not be that contextual which will result in fewer clicks and thus lower revenue.