This data is for $2NL. It will take a little math, but you should be able to figure out which one rakes you more.
Full Tilt rakes pots at 6.67%, max of $2, and they give you 27% rakeback plus Iron Man.
Stars rakes at 5%, max of $2, and they have the most complicated rakeback program ever.
Cereus, Carbon, and Bodog rake at 5%, with a $3 max rake, and they provide ~35%+ rakeback.
Cake is the same as full tilt (6.67% max of $2), but with 33% rakeback.