I run both, and at times I've made both my featured ad. What I've discovered with my site is I do much better with adsense (about 10 to 20x better). Each site is different, and your approach to affiliate ads are different to adsense ads. Meaning, with adsense, your goal is to get a click, with affiliates, your goal is to get a sale (cpa). 1,000 affiliate clicks don't pay unless they convert, 1,000 adsense clicks will pay every time.