AdSense vs. affiliate comes down to at least in part, the intent behind why someone came to the site. What keyword led them there? If it was a "buy" keyword (brand derivative, model number, something with buy, order, send in it) and the person is more likely to want to buy now then affiliate programs will likely pay more. In that case, the site needs to be geared to sell. For a more general site with a different keyword referral set, AdSense is likely to be more profitable. It always comes down to testing of course but if you are getting buyers, then aff links should probably perform better.