To me, Signs is a much better film. While the Aliens come and there are crop circles (let's face it, that part is a little ludicrous), we see how the faith of one man becomes restored based on a prognostication by his dying wife that the former Preacher has to recognize, thereby getting his life back. Here, with Knowing, we have a Minister's son who after his wife dies, thinks that "Shit Happens" and there is no pre-ordained determination of how things happen and comes to believe only through some preprinted numbers on a sheet of paper that indicate to him that God has a very specific plan. Oh yeah, and there are Aliens who just happend to have gotten God's memo and nab some kids to prepopulate another world with Earth's children. We didn't see any pre-existing colonies like we did at the season finale of Battlestar Gallactica though. (I'm just saying.)
So the payoff for Mel Gibson's character is that he gets his mind and his family back and get's to see the world through eyes of faith. The payoff for Cage's character is that his kid survives, he hopes, and then he burns to a crisp. And Ebert says that Signs didn't pay off?
Lastly, I'm not buying that you either A) think that there is determinism or B) think that things are accidental. I lie somewhere in the middle, personally. Just because I might believe in God, doesn't mean I think that fate and plan are tied irrevocably to that belief in God. But, that is another story.