Fujifilm XP90 has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor . On the other hand, Canon SD780 IS has a 12.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the XP90 and SD780 IS sensor size comparison.
Fujifilm XP90 and Canon SD780 IS 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 SD780 IS has 32% larger pixel area (2.34µm2 vs 1.76µm2) compared to Fujifilm XP90, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.