I played the S+ flex and the S pretty interchangeably, did not notice a huge difference. Regular S are 5g lighter, but didn't produce a measurably different ball flight.
Compared to s300 and even the regular KBS Tour, which I also played, I think the C Tapers are superior for me. They feel smooth, and the the trajectory is a flatter climb to apex. Unless I was hitting into a moderate headwind the ball did not climb wildly or balloon. Still easy enough to stick anything 7i and up, and you probably won't spin back 9i shots off of the green.