Personally I wouldn't go anywhere near those kind of sites, they seem way too scammy in my opinion or at least the potential to be scammy. If you really have to then clearly bitcoin is the best way to pay if these girls (or guys - joke) actually accept bitcoin. Don't put your credit card details anywhere near these sites.
One advantage of credit cards would be that, when the site gets hacked, and your credit card gets used by a carder, then you can charge back the stolen amount. When the website loses all bitcoins then they are gone.