I'd use epals because....

In my case, I work with alternative kids. Epals would be easier for me to monitor. I also think that if I gave them the website for Kidlink, they would do more fooling around on it than actual learning. With a pen pals website, I can easily monitor their letters, language and ideas, and I can also ensure that my students are working by having a letter to show for it. With my kids, I need to see that they are making progress and doing work. Also, I can have a bunch of letter to show their parents their progress/problems. So, for me, Epals would be a better fit.