The New York Times very briefly looks at this question and answers:
Sex in advertising is generally thought to be more useful in selling to men than to women. But a study soon to be published in The Journal of Consumer Research finds that this effect is reversed when emotional intimacy justifies the sex.
In one experiment, the researchers found that women preferred a sexually explicit watch advertisement when the watch had a bow around it and was described as “a gift from a man to the special woman in his life.” But such positioning hurt the ad’s appeal to men. Drawing on previous research in sexual psychology, the authors note that women are more likely to “need the justification of relationship commitment for sexual behavior” and that men “typically felt quite uneasy about having to part with substantial pecuniary resources in a dating context.”