Olympus TG-5 has a 12.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features TruePic VIII processor. On the other hand, Nikon W300 has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized sensor .
Below you can see the TG-5 and W300 sensor size comparison.
Olympus TG-5 and Nikon W300 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 Olympus TG-5 has 32% larger pixel area compared to Nikon W300, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.