Both Panasonic S1H and Nikon D5300 have 24.0 MP resolution sensors but Panasonic S1H's sensor is Full frame (35.6 x 23.8 mm ) and Nikon D5300's sensor is APS-C (23.5 x 15.6 mm ).
Since Panasonic S1H's has a larger sensor area with the same resolution, this means that it also has a larger pixel area hence better light collecting capacity for a given aperture compared to Nikon D5300.
One other difference between these two cameras that is worth mentioning is that Nikon D5300's sensor doesn't have an anti-alias (Low-Pass) filter. Removing anti-alias filter increases the sharpness and level of detail but at the same time, it increases the chance of moiré occurring in certain scenes.
Below you can see the S1H and D5300 sensor size comparison.
As seen above, Panasonic S1H has a 2.3x Larger sensor area than Nikon D5300. Larger sensors give photographer more control on the depth of field and blurry background compared to smaller sensor when shot in same focal length and aperture.