Leica S2 has a 38.0MP Medium format (45 x 30 mm ) sized CCD sensor . On the other hand, Hasselblad X1D has a 51.0MP Medium format (44 x 33 mm ) sized CMOS sensor . Hasselblad X1D's sensor provides 13MP more than Leica S2'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.
Below you can see the S2 and X1D sensor size comparison.
Leica S2 and Hasselblad X1D have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.