FujiFilm F70EXR has a 10.0MP 1/2-inch (6.4 x 4.8 mm ) sized CCD sensor and features EXR processor. On the other hand, Olympus TG-4 has a 16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features TruePic VII processor.
Olympus TG-4's sensor provides 6MP more than FujiFilm F70EXR'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 F70EXR and TG-4 sensor size comparison.
FujiFilm F70EXR and Olympus TG-4 have almost the same sensor size so none of them has any significant advantage over other in providing control over depth of field when used with same focal length and aperture.