X100 has the largest sensor and should give the best overall image quality, amazing camera, built like a tank and looks beautiful. However, only has a fixed lens which may or may no matter to you, but worth considering what you want to use it for.
RX100 second largest sensor and gets amazing reviews too.
I would steer away from the other two just because of their small sensors.
I'd personally choose the X100 and live with its lack of zoom, but either this or the RX100 won't disappoint.