Canon Elph 115 IS has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features DIGIC 5 processor. On the other hand, Nikon S1200pj has a 14.0MP 1/2.3" (6.17 x 4.55 mm ) sized CCD sensor .
Below you can see the Elph 115 IS and S1200pj sensor size comparison.
Canon Elph 115 IS and Nikon S1200pj 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 Nikon S1200pj has 14% larger pixel area (2.01µm2 vs 1.76µm2) compared to Canon Elph 115 IS, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.