I prefer the big bang theory because evidence like background EM radiation and the measurable expansion of the universe supports it. I don't actually believe that there was nothing before that "one spec", for the reason you stated. But we just have absolutely no way (currently) to empirically determine what existed before this thing we call the universe did. And I think in that respect, science and faith are at least not at one another's throats, because when grappling with questions that have the enormity of "what existed before the universe did?", then each theory, each belief, is exactly as valuable as the last.