Sony T90 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Nikon A10 has a
16.0MP 1/2.3' (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the T90 and A10 sensor size comparison.
Sony T90 and Nikon A10 have the same 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 Sony T90 has 32% larger pixel area compared to Nikon A10, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.