Below you can see the front-view size comparison of the Pentax WG-3 GPS and Pentax WG-10. The Pentax WG-10 is clearly the smaller of the two cameras. Its body is 9 mm narrower, 5 mm shorter and 4 mm thinner than the Pentax WG-3 GPS.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.