Canon D30 has a 12.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features DIGIC 4 processor. On the other hand, Nikon W300 has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized sensor .
Below you can see the D30 and W300 sensor size comparison.
Canon D30 and Nikon W300 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 Canon D30 has 32% larger pixel area compared to Nikon W300, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.