If you know the difference in usage between the first and second conditionals, then this difference is illustrated in your sentences. The first one is a hypothetical situation e.g. If you saw me steal a chocolate bar, you wouldn't go to the police, would you? (2nd cond'l) The second is a real situation e.g. I admit that I stole a chocolate bar, but you won't go to the police, will you? (1st cond'l)

There *is* a difference. The conditional (would) sounds more "pleading" or "requesting"; it's more hypothetical, and it's also a more humble form. "Will" sounds more direct. For an image, if you think of a gangster holding a gun to your head, he would say "You won't *really* go to the police, will you?" because it implies that he is *telling you* not to go to the police, even though he sounds as though he's *asking* you.