I find that it is fair to say men benefit from casual sex encounters more than women.
In the Penguin publication the "Red Queen" by Matt Ridley, he writes:
Throughout our evolutionary history, men and women have faced different sexual opportunities and constraints. For a man casual sex with a stranger carried only a small risk - infection, discovery by the wife - and a potentially enormous reward: a cheap addition of an extra child to his genetic legacy. Men who seized such opportunities certainly left behind more descendants than men who did not. Therefore, since we are by definition descended from prolific ancestors rather than barren ones, it is a fair bet that men possess a streak of sexual opportunism. Virtually all male mammals and birds do, even those that are mainly monogamous... men are more likely to be tempted by an opportunity for casual sex than women.
So, Ridley states that because men who were more promiscuous left more offspring. Modern men too posses a streak of sexual opportunism inherited from their ancestors.
On the other hand, he writes of women:
Women are likely to be different. Having sex with a stranger not only encumbered a Pleistocene woman with a possible pregnancy before she had won the man's commitment to help rear her child, but it also exposed her to probable revenge from her husband if she had one, and to possible spinsterhood if she did not. These enormous risk were offset by no great reward. Her chances of conceiving were just as great if she remained faithful to one partner and her chance's of losing the child without a husband's help were greater. Therefore women who accepted casual sex left fewer rather than more descendants, and modern women are likely to be equipped with a suspicion of casual sex.
This provides an evolutionary explanation as to why the two sexes behave differently. However, Ridley does account for social pressures writing:
A modern women is exposed to pressure from men to be sexually uninhibited, but she is also exposed to the same pressure from other women. Likewise, men are under constant pressure to be more 'responsible', sensitive and faithful - from other men as well as well as from other women.
So he also acknowledges that this could be skewed by people pressuring women to be more promiscuous and men to be less so. However, I found conflicting evidence to one of Ridley's assertions: that men are not as pressured by other men to avoid casual sex. Personally, I agree with the conflicting evidence, which can be found here under the title: "Social Psychology and Human Sexuality: Essential Readings", page 156. I quote:
Of particular interest was the fact that the male peer groups agreed to support each other in their efforts to obtain sexual experiences during the vacation, whereas the female peer groups were more likely to agree to support each other in refraining from sex.
Discussion of above evidence Taking the arguments and research above into account, I would say that in terms of genetic legacy men benefit more in that they are able to have more offspring from casual sex, without having to raise them. Socially it is difficult to say, for example, women, who are caught having casual sex, may be rejected by their partners, who don't want to raise a child that isn't there own, and thus have no support in raising the potential offspring. Also, looking at the evidence above, it seems that their friends don't support casual sex and thus they may be scolded or even rejected by them. However, I have inferred this from the evidence and cannot say with certainty. There could also be repercussions for males, for example, would a prospective female partner want to reproduce with a male whom she knows has had casual sex with multiple women? What's to say they won't do it again? So, it is possible that social repercussions also would happen for men.
Conclusion As a final concluding argument, I will say: casual sex has more genetic benefits for men, as it is an easy opportunity to extend their genetic legacy. The full social repercussions are unclear for both sexes, however, it is likely both sexes face negative repercussions, if found out. Both sexes can potentially face negative consequences but the male will always earn the greatest potential benefit from casual sex: new offspring, with no parental investment on his part.