I'm not a great speaker myself (even in my native tongue!). I find writing easier as it's easier for me to express what I want to say. Obviously for some it's the opposite. As for foreign languages, it depends on what kind of language it is. For example, I probably wouldn't be able to write Arabic as well as I speak if I were to learn it for the first time. If the alphabet is similar to English (like French or Spanish), then it will be a bit easier to write than to talk (from personal experience).