What are the effects of casual sex on men versus women? There is a lot of research citing that men are more physically primed for sex than women. Graziottin (2004) discusses this difference and other differences of strength and vulnerabilities between the sexes:


  The clinical correlate of the neurobiological condition is that men have a stronger, more biologically and genitally focused sexual drive, expressed more as lust (7). Women tend to have a romantically driven sexual drive with a more relational expression and emphasis on intimacy (6,7). Women have a stronger oestrogen priming of two other basic emotions command systems, the fear- anxiety and the panic with separation-distress, which contribute to and modulate their parenting abilities and social bonding skills (2,19). The gender-based different biological modulation of seeking pathways in men and women may be an important contributor to different desire vulnerability in the sexes, both in the early phases of a relationship and later stages of a long-term relationship (34,35). 


Is it really fair to say that men are more inclined to benefit by casual sexual encounters than women, or is this a presumption stemming from social-stereotyping?
One factor that should be considered is the culture surrounding casual sex and the social judgments that men and women may experience as a result of casual sex. Conley, Ziegler, and Moors (2012) report a series of experiments conducted on an American university campus that show that women who accept offers of casual sex are perceived more negatively on a variety of dimensions than men. In their experiments:


Subjects judged women who accepted offers of casual sex as being "less intelligent, less mentally healthy, more promiscuous, less competent, and more risky" than men who accepted offers of casual sex.
When subjects imagined a hypothetical offer of casual sex, men were more likely to accept than women. Subjects were given a series of questionnaires to examine their attitudes towards offers of casual sex. A mediation analysis indicated that "part of the reason that women are less likely to accept casual offers than men is that women perceive that they will be evaluated more negatively for accepting the offer (or more positively for rejecting the offer) than men do."
Similar results were found when subjects recalled a recent offer of casual sex, and imagined the reactions of people had they accepted the offer.


Thus, social stigma seems to play a significant role in how men and women perceive casual sex, which may explain the relative willingness of men and women to engage in casual sex. This particular set of social stigmas will certainly not be universal across cultures, and the point of this answer is not to suggest that the experiences of American college students are universal. What is likely to be universal is the idea that the culture surrounding casual sex will have a direct impact on how men and women choose to engage in casual sex.