@Phil
That is very good point about Chinese. Before I only considered what kinds of teachers I'm having now and how do I feel about them, but my context is studying Chinese and there certainly are a lot more female teachers than male. This should also depend on the language you're studying. In Japanese men and women talk very differently and if I was studying Japanese at the beginner level that I am in Chinese now, I would exclusively go to male teachers. The difference is so great and when learning a language you must mimic other peoples word choice, intonation, grammar patterns, etc. If a male learner does this only with female teachers, in a language like Japanese, the results can be funny. It is also not a question about the teachers or tutors ability as I'm sure they'll try to speak in general way, but how a person talks is so integral to who they are, that they won't just be able to change it to that kind of extent. And would a learner want to listen to such unnatural speech anyway..
I also think this must be the case for other languages like Thai, Vietnamese, and maybe Korean too. I hear they might use different pronouns, verb forms, etc. based on the speakers gender.
Because of my experience with Japanese, before I started having italki lessons, I asked two professional teachers if they thought men and women talked in Mandarin differently and they convinced me that there are really no big differences like that with the greatest probably being that women tend to use sentence ending particles like ĺŚ, ĺ, ĺŚ, and ĺ a bit more. After that I was happy to use female teachers, but had they told me that there were big differences, I would have exclusively gone to male teachers in the beginning and began taking a lesson now and then with female teachers a little later.