Should he pray in the mosque where there are some innovations or in the prayer-room in his building?
Question

I am a student at an Islamic University in Malaysia. I am very keen to pray in congregation as much as I can in the Jaami‘ (main mosque), but I have some reservations about what some of those who lead us in prayer do of things that are not in accordance with the Sunnah (according to my knowledge), such as reciting du‘aa’ in unison after each prayer, and mixing the adhaan with the Qur’an sometimes, and making the final prostration lengthy in order to say du‘aa’, and singling it out for that purpose. In contrast, we have prayer-rooms in the student residences in which prayers are held in congregation, the adhaan and iqaamah are given openly, and one of the students leads the prayers, and none of the innovations mentioned above are committed. Which of the two places is better to pray in?.
Praise be to Allah.Offering the prayer in congregation in the mosque is obligatory for men who are able to do it, according to the more correct of the two scholarly opinions, because of evidence mentioned previously in the answers to questions no. 8918 and 8918 . 
If you can hear the call to prayer, then what you are required to do is to pray with the congregation in the mosque. You should advise the imam and tell him what is Sunnah; then if he insists on offering du‘aa’ in unison, do not join in the du‘aa’. See questions no. 10268 and 10491 .
What is meant by hearing the call to prayer is that if the individual can hear the adhaan in a normal voice without a loudspeaker, if the mu‘adhdhin raises his voice, and there is no wind or noise, or other things that may affect one’s ability to hear it. 
If you cannot hear the call to prayer, then it is permissible for you to pray in the prayer room in your residence; in that case you should weigh up the pros and cons, such as if your attending the mosque will result in your having contact with ordinary people and calling them and teaching them. In that case, it is more important for you to pray in the mosque than to pray in the prayer room in the student residence, and so on. 
And Allah knows best.