[LennonCook]

Originally posted by Kestrel Daystar: It wets your appetite

No, it doesn't

And, as phillip said, rerolling gives you a different total, while + and - can only move your points between different stats. Many people use a combination of these: they reroll until they get sick of it, and then adjust this based on their character. On the other extreme, some people ignore the fact that you can do either, and take the first set of stats they are given (to avoid powergaming their stats).