It seems that the vast majority on the poll list their study as Northern Mandarin vs. Southern. By the standards that led to that distinction, what is the difference between the two? Are we talking something like 普通话 versus 上海话, or is there some other standard being compared here? Either way, living in Wuhan and learning a largely Wuhan-inflected idea of 普通话, I feel a bit dishonest answering either, though I went with Northern because of the 普通话 thing. Perhaps it would have been better if it had been distinguished as Putonghua vs. non-standard Mandarin or somesuch thing, unless I'm missing a key distinction between Southern and Northern Mandarin...