I choose MFL because I did Spanish and it was my hardest AS and I dropped it. But it is totally subjective and people only really know about the subjects they do so it is hard for anyone to say.
How is English hard? All you do is make stuff up and vaguely link it to a quote. Come to think of it that's what almost all humanities seem to be like
Making stuff up. There's your answer. What are you supposed to come up with? The questions and mark schemes are extremely vague and subjective and there's no clear way to answer the questions. There is also very little or no course content to help you answer the questions.
Out of the humanities I only took geography at GCSE, but it was much, much easier than English. There was two years worth of content to memorise that could be used as a basis for answering a question and there was also a clear way to structure an answer. The questions were a lot more closed, more guided and shorter than English. The topics covered were a lot more interesting and had clearer points and conclusions.