Sigma SD10 has a 3.0MP APS-C (20.7 x 13.8 mm ) sized CMOS (Foveon X3) sensor . On the other hand, Sigma SD14 has a 5.0MP APS-C (20.7 x 13.8 mm ) sized CMOS (Foveon X3) sensor .
Below you can see the SD10 and SD14 sensor size comparison.
Sigma SD10 and Sigma SD14 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 Sigma SD10 has 35% larger pixel area compared to Sigma SD14, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.