I think it depends on what kind of backlinks you need, .edu, .gov and pr4 or .....
You can place what you are looking for in the search box and hit enter. You later see a bunch of gigs and you need to hit the "popularity" tab to see the one people use a lot. That is the best among the crowd. You then check the feedbacks from users. Pick the one you are comfortable with. If you don't like the result, get the money back.