I use Reddit to find penpals because I find the quality of posts and responses is higher (though Slowly so far has been excellent as well). I've used a handful of other penpal sites but have hated how so many are set up like social media profiles (with photos and status updates and such). One thing I like about other sites is there is more of a mix of nationalities. Reddit has quite a lot of American users, not that I don't like Americans, but it's nice to have a variety. My main intention is to form long term, deep friendships based on the written word via email. I really don't know what my ultimate feature would be. I'm generally not a fan of all the bells and whistles some penpal services have (apart from Slowly's simulated snail mail, that's fun). I like straightforward setups.