One advantage is that it's been around since 1997, long enough to have a base of over 5 million users, even though it is a lesser-known site.You can also view the site in Spanish or Portuguese, which may be helpful if you are bilingual.
Since free sites have no barriers to entry, they are sometimes used as a way for scammers to set up free profiles to ask for money.
The point of the Facebook connection is that you can meet people who are friends of people you already know.
A lot of dating sites that were free at one point are no longer free to use now; for example, Match and Lava Life.
For example, you can play games, send virtual flowers and deliver e-cards to those you are interested in connecting with.
Oasis Active offers the option to search for romantic partners or platonic friends.
Soul Mate Find is geared toward people who are trying to find life partners.