Pentax K200D has a 10.0MP APS-C (23.5 x 15.7 mm ) sized CCD sensor . On the other hand, Pentax K100D S has a 6.0MP APS-C (23.5 x 15.7 mm ) sized CCD sensor .
Below you can see the K200D and K100D Super sensor size comparison.
Pentax K200D and Pentax K100D S have sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture. On the other hand, since Pentax K100D S has 66% larger pixel area (61.08µm2 vs 36.75µm2) compared to Pentax K200D, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.