Two of my closest friends hate eachother?

What do you do when two of your closest friends who are totally opposite in personality, talk badly about eachother to you and try and make you feel bad about having them in your life? Both of them ask about eachother and ask how they are but always comment negetively towards what I say. Both of them don't understand eachother and eachothers lives but feel they should judge them. When I have made arrangements with one of them and the other wants to meet me they will try and make me re-schedule and judge the situation and make it seem like I should favour one over the other. I try to please both of them by being a good supportive friend but they make it hard for me because i feel like they are always making me choose.....what do I do?