Nikon B700 has a
20.0MP 1/2.3 (6.17 x 4.55 mm ) sized BSI-CMOS sensor . On the other hand, Olympus SP-590 UZ has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Nikon B700's sensor provides 8MP more than Olympus SP-590 UZ'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 B700 and SP-590 UZ sensor size comparison.
Nikon B700 and Olympus SP-590 UZ have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.