Canon SX200 IS has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Nikon B700 has a
20.0MP 1/2.3 (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Nikon B700's sensor provides 8MP more than Canon SX200 IS's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the SX200 IS and B700 sensor size comparison.
Canon SX200 IS and Nikon B700 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 Canon SX200 IS has 68% larger pixel area compared to Nikon B700, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.