Actually, I believe that you can earn more miles on Greenpoints. Purchases earn 20 points/$, and points convert to miles (DL and AS only) at 5:1 (or, effectively, 4 miles/$). Greenpoints also has a lot of Click & Earn opportunities which allow you to acummulate points without purchases. On the other hand, I believe that ClickRewards has much better service (albeit fewer freebie offers), and Clickmiles redeem to more FF programs. The redemption rates on MyPoints are not as good.