Not sure, i was using a site before called j-list but the closed their site. Except truelovejapan website, i am not really sure. The others are not specialized for japanese people so i am not sure... i am satisfied so far so i dont need to spend time to search else where.
At first because it's free but after trying their site, i really liked the fact that i can meet people that has been verified. Since i am in japan and not there for chatting, i need to meet real people, this is so useful for me :)