Totally different cameras, SX260 small sensor, S100 larger sensor.
Go to a camera store and try them, they is going to be a difference in feel and the controls.
The SX260 has a long zoom range, built-in ***, but slow autofocus and not so good high ISO performance.
The S100 has better performance, but a shorter zoom range and no ***. Tradeoff to get the features you prefer. You are going to like either if you buy it for its strong points, and if it feels comfortable to you.