That isn't the question though, once you know you are living in a simulation what happens? This was a very interesting question that was raised in the TV show Caprica (a Battlestar Galactica prequel series). If you know it is a simulation then you can just do what ever the heck you want, reboot/restart when necessary. Doesn't make for interesting cinema or literature as the question of future value / future outcome vs present action / inaction is what creates tension.

Probably the best argument there is Occam's Razor. A heuristic it may be, but it has proved useful many times. Though I've often wondered if it truly has that much cosmic power, or if it becomes useless at that scale.