One disadvantage of the "S" models that no one ever talks about is that since they are shorter they have substancially shorter rails underneath. That means you can't shove your saddle as far back as you can with a men's model (non-S).

When I went from a B17S to a B68 (non-S) I was surprised and delighted at how far back I could now move my saddle- a full 2" further back! It put my center of gravity in a MUCH better place and helped me eliminate that feeling of falling forward. My weight is now balanced further back and it feels SO much better.