Both camera look similar form outside but do they differ from inside or almost have same core specification, take a look at the core difference below…
Unfortunately both camera are using 16 Mp APS-C X-Trans CMOS II Sensor and EXR II image processor, hence the image quality will remains same from both the camera.
Both camera share same Fujinon 23mm f/2 Fixed Focal Length Lens,
Again in AF system there is no change, Both the camera shares same Hybrid AF system and AF points, so again no change here.
Since the sensor is same and image processor is also same, by implementing new image processing algorithm, Fuji is able to get ISO upto 51200. But it doesn’t mean you will see significant difference in the image quality of both the camera.
A redesigned shutter mechanism, which is now entirely electronic, also delivers quickened shutter speeds up to 1/32,000 sec.
Built-in WIFi to share your files easily without any physical pain.
Verdict: If you are a owner of X100S than wait for Fuji X200, since there is no change in the sensor, image processor and lens of both the camera.