The main issue with these cam scripts is that they are poorly written which slows down your site and it is not optimized for search engines, in some cases, it is very hard to get any SERPs at all. I built a lot of projects with Roboscript and Econfirm and the latter would not rank for any good keywords, no matter how hard I try but with the Robo you can do way more customizations, et cetera. I would stay away from any freemium tools, as already been suggested here.