Personally, I would prefer a leader that did not have a strong religious belief, or any religious belief at all. Religion is a divider, not a uniter, and a leader needs to be a strong uniter. I'd prefer that the leadership could listen to all voices and make an educated decision on any matter. But there is the key word. Educated.
As studies have shown, the more education an individual is able to get, the less likely they are to fall back upon religion or practice religion religiously (pardon the pun). I think a highly educated person in a position of leadership is the most important. I think Bush is a perfect example of the point I'm getting at!