Below you can see the front-view size comparison of the Fujifilm X-H1 and Panasonic S1R. The Fujifilm X-H1 is clearly the smaller of the two cameras. Its body is 9mm narrower, 13 mm shorter and 11 mm thinner than the Panasonic S1R.
The chart below depicts how two cameras compare with average dimensions of the cameras in their class.