FujiFilm Z700EXR has a
12.0MP 1/2-inch (6.4 x 4.8 mm ) sized CCD sensor and features EXR processor. On the other hand, Fujifilm Z900EXR has a
16.0MP 1/2-inch (6.4 x 4.8 mm ) sized EXRCMOS sensor and features EXR processor.
Below you can see the Z700EXR and Z900EXR sensor size comparison.
FujiFilm Z700EXR and Fujifilm Z900EXR 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 FujiFilm Z700EXR has 32% larger pixel area compared to Fujifilm Z900EXR, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.