Free will is completely necessary within religion, with the most heavy emphasis I've experienced being placed upon Christianity. The Christian god is said to have created Adam and Eve, and given them free will. Were they perfect creations of God? No, apparently not. Their intelligence was incredibly limited and God knew that this free will would bring them into pain and sin, yet he gave it to them anyway. He knew what path every single person on earth would take because of his choice. The incredible freedom supposed of God's gift of mankind's free will is limited in itself because of creating a rather unintelligent human race.
If a person in today's world hears of Christianity, but is a Muslim who has been firmly indoctrinated in their faith - there is a good likelihood that Christianity may never really even cross their mind as a possibility of the religious truth. The problem is within the idea of "informed choices". There is no amount of supposed available knowledge in existence that could convince mankind, as a whole, of a single faith being the only possible valid religion. Even myself, living within the realm of Christian belief for 19 years did nothing to stop me from researching alternatives and doubting any religion's accuracy.
Free will is free only while knowledge is. Our lives and "choices" are deterministic. Our limited knowledge directs our choices to take the paths they do. If the only thing existing in defense to Christianity is faith alone and objective knowledge of the truth of religion in the grand scheme is impossible, then free will is a misnomer in itself. There is no such thing as "free will", and instead it is limited subjective will - at best. This informed decision of choosing Christianity as a factual religious belief is no more supported or valid than choosing Zoroastrianism. Informed choice simply relies on which religion impacts you the most.