Speaking, most definitely. Not only do you have to think on your feet, but you have to be careful about your pronunciation in order to not confuse to listener completely. Reading and writing are actually quite easy for me, because I can take my time and look words and examples up in order to help myself along. You don't get to take it that easy when talking, unfortunately, since the point is to carry out a conversation. You'd probably end up annoying your conversation partner if you even tried.