Although the recruitment of online survey participants through paid social media advertisements is becoming increasingly common among political scientists, we know little about how the content of advertisements used to draw the attention of social media users influence the recruitment process. Researchers advertising on social media use various strategies to convince users to participate in their surveys, such as asking for help, mentioning the theme of the survey, or offering material incentives. Our study compares the effects of these approaches relying on 22 advertisements campaigns conducted in Turkey and Spain recruiting more than a total of 30,000 respondents. Our paper documents important trade-offs that the advertisement content creates regarding the cost and the sample composition. We find that incentive-based advertisements can produce samples that are highly representative; however, this also depends on the type of the incentive. Thematic advertisements, which mention the political content of the survey, consistently return the cheapest samples, yet men, older people, college graduates, politically interested people, and strong partisans are highly overrepresented in these samples. On the other hand, we do not find substantially significant effects of advertisement content on response quality. Our paper concludes with practical advice on which advertisement content to use depending on the goal of a particular study.