Doctor – heretic expert or frum less expert

Igros Moshe (YD IV #08.01 pg 166)  Is it preferable to use an expert doctor who is a heretic or a frum doctor who is not as excellent a doctor? This question does not need a psak since the Torah permits treatment by doctors, and the Rambam  and most of the Rishonim hold it is even an obligation, so surely one should go to the specialist doctor , even though he is a heretic or even non Jews  who are idolators in our time who are not suspected of killing on purpose, it is necessary to. And it is not appropriate to be concerned that G-d sent his cure through a heretic, because concerning cures we were commanded not to trust in a miracle.as long as it is possible to be cured with medicine that G-d created for the healing of the sick. This expert is more knowledable about the sicknesss and the medicines. However since it happens at times that a doctor errs, it is nessary to also pray to G-d that he won’t err and that he be the agent of cure.  We find in the gemora that our Sages went to non Jewish doctors and heretics who it was certain they would not kill them.  However if the doctor is a missionary then he is prohibited even if there is no other doctor.  In fact most doctors, even non Jews and heretics will simply do their job and not try to missionize and thus there is no need to be concerned with this . However if it is known that if he is a missionary it is prohibited to be cured by them,