Fujifilm X100F has a
24.0MP APS-C (23.6 x 15.6 mm ) sized CMOS X-TRANS III sensor and features X-Processor Pro processor. On the other hand, Sigma DP1 has a
5.0MP APS-C (20.7 x 13.8 mm ) sized CMOS (Foveon X3) sensor .
Fujifilm X100F's sensor provides 19MP more than Sigma DP1's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Another difference between these two cameras is that Fujifilm X100F's sensor lacks anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the X100F and DP1 sensor size comparison.
As seen above, Fujifilm X100F has a 1.3x Larger sensor area than Sigma DP1. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.