My experience is that pay sites are geared most towards signaling professionalism and (moderate) wealth -- which is often shorthand for 'adult', and therefore useful. However, in my experience OKCupid has provided better signaling for intelligence and thoughtfulness, simply because it allows users to write commentary on any question you answer. Most users do not take advantage of this, but looking for 'explained answers' is one of the most useful metrics I have found on any dating site.