A bunch of cautionary remarks seem indicated.
First, belief that one’s religion is the One True Faith is hardly limited to extremists. Very rational Jews here, very rational Moslems here in the past, and numerous flavors of very rational Christian, including myself, would so maintain.
The analytical point here is that, unless you choose to wear blinders to the agreements between tenets of your own belief system and those of other systems, you are forced to realize that there is an underlying partial metaphysic on which they all are based, fleshed out differently according to the social and cultural biases, the semantic/conceptual systems, and so on, in which each set of believers finds itself located. For example, Christianity in Western culture need not explain away the Great Mandala and the cycle of rebirth; they’re not a part of Western civilization, except as recent imports accepted by a relative few. Buddhism is forced to confront those issues head-on, however, owing to the Hindic metaphysic in which it was born and the related East Asian worldviews it has spread through. Zen as the extreme in do-it-yourself enlightment is probably the clear product of the migration of Dhyana concepts from nascent Mahayana Buddhism through Chinese thought to Japanese practicality and self-reliance. Which is why it is the aspect of Buddhism most attractive to most Americans who investigate it.
My own stance is that every religion is founded on some valid insight into the nature of God, the ultimate, and one’s proper place in the overall metaphysical structure of the cosmos, overlain by suppositions, imaginings, and pseudo-logical conclusions drawn from this to provide an organized-religion structure “with all the answers.” This includes my own Christianity. However, what Christianity has over the others is that its believers, including me, believe Jesus to have been God incarnate as a human being, walking and talking with other people. In the metaphors He chose to explain His understanding, and in the life He lived and called His followers to live, one finds one’s closest approximation to the True Path to God™.
Finally, I get the distinct impression that most people use “faith” to mean “believing what I don’t know to be true but for some reason or other, valid to me, accept as the truth.” This is the exact mirror image of the flawed “evolution is just a {sneeringly} theory” comment of fundamentalists. Faith in the sense I use it is synonymous with trust – having had some experiential reason to accept God as an entity to and with whom one may have a relationship, one puts one’s trust in Him. The question of relative certitude is in a completely separate dimension here: You might as well ask whether the law of inverse squares or your love for your beloved is truer. The terms are coordinate but skew off when one attempts to relate them, owing to distinct meanings in different contexts.