Nikon D2Xs has a
12.0MP APS-C (23.7 x 15.7 mm ) sized CMOS sensor . On the other hand, Nikon D2Hs has a
4.0MP APS-C (23.7 x 15.5 mm ) sized JFET sensor .
Nikon D2Xs's sensor provides 8MP more than Nikon D2Hs'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 D2Xs and D2Hs sensor size comparison.
Nikon D2Xs and Nikon D2Hs have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.