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, Ricoh WG-5 GPS has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor .
Below you can see the TG-5 and WG-5 GPS sensor size comparison.
Olympus TG-5 and Ricoh WG-5 GPS 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 Ricoh WG-5 GPS, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.