Here is a 50+ page report comscore did on the industry….
Plentyoffish produces more dates per user than any other site, and people say Plentyoffish has the best matching system in the industry 
http://www.plentyoffish.com/US_online_Dating_report.pptx
•The U.S. dating website landscape is very competitive; Plenty of Fish, eHarmony, and Match are the current market leaders in the category.
–Plenty of Fish ranks 3rd, behind eHarmony and Match for unaided brand awareness.
–Plenty of Fish leads all competitors with the highest proportion of active users, but eHarmony and Match have higher overall aided awareness levels.
–Plenty of Fish leads competitors as a source of the highest number of dates during the past two years (on average).
–Taken together, there is some evidence to suggest that Plenty of Fish has become more popular during the last six months while eHarmony and Match are “older” sites: although awareness is higher due to length of time in the market, usage may be starting to drop off.
•Competitive ratings and analysis identified the relative strengths and weaknesses of Plenty of Fish, as experienced by current and recent users.
–Relative Strengths:
•Lots of profiles available, with no limits placed on the number of matches.
•Easy to use and to maintain profiles.
•Good place to meet people who share the same culture/religion, who are “similar to me”.
•High user satisfaction and likelihood to recommend the site to others.
