I am not sure I get what you are talking about, but I voted "I have a reason to Believe" because I am taking it as a larger concept, and therefore it is much more important to me to have a reason to believe in something, than to have no reason to doubt it.
I mean, I have no reason to doubt a whole miriad of things...but why should I believe in any of them unless there is some reason?
In other words: Why make stuff up?
My gut reaction was that there was no choice for 'I have no reason to believe'. Without more context, I for one, won't understand what you're getting at.
DDR at least give some detail on what the heck you're talking about.
My point was:
If I have a reason to belive then I have minimum one reason to believe.If I have no reason to doubt then I have minimum all the reasons to believe.The expression "I have no reasons to doubt" is much wider and more general and it incorporates the expression "I have a reason to believe" in its self.