Nikon S6100 has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Expeed C2 processor. On the other hand, Canon SX150 IS has a 14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Digic 4 processor.
Below you can see the S6100 and SX150 IS sensor size comparison.
Nikon S6100 and Canon SX150 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 SX150 IS has 14% larger pixel area (2.01µm2 vs 1.76µm2) compared to Nikon S6100, it has larger pixel area to collect light hence potential to have less noise in low light / High ISO images.