Below you can see the front-view size comparison of the Pentax K-S2 and Fujifilm X-T10. The Fujifilm X-T10 is clearly the smaller of the two cameras. Its body is 5 mm narrower, 8 mm shorter and 32 mm thinner than the Pentax K-S2.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.