Both Fujifilm S2 Pro and Nikon D70 have 6.0 MP resolution sensors but Fujifilm S2 Pro's sensor is APS-C (23 x 15.5 mm ) and Nikon D70's sensor is APS-C (23.7 x 15.5 mm ).
Since Nikon D70's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Fujifilm S2 Pro.
Below you can see the S2 Pro and D70 sensor size comparison.
Fujifilm S2 Pro and Nikon D70 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.