I have both.. and I have small hands. It's hard to say which one works better for anyone until you pick them up.
On paper, the S2 is slightly bigger, and I would agree that the grip of the S1 feels smaller (Hennings on both). But I like the way I grip the S2 better... the shape feels better and I tend to try to regrip it less.
Of course... I shoot the S1 bettter, so the only true answer is to shoot them both and figure out which one suits you the best