I've noticed that a lot of people like to focus on studies that find that women who had sex with men with and without their foreskin experienced different levels of sex. That basically means you're looking for an experienced women which can be a bit difficult to find.
I'd like to propose an easier way to find a link between sexual pleasure and circumcision. Divorce rates. Compare the two groups and see who wins out. After all, sex has a lot to do with divorce.