Fujifilm XP90 has a 16.0MP 1/2.3" (6.17 x 4.55 mm ) sized BSI-CMOS sensor . On the other hand, Pentax Q-S1 has a 12.0MP 1/1.7" (7.44 x 5.58 mm ) sized BSI-CMOS sensor and features Q Engine processor.
Below you can see the XP90 and Q-S1 sensor size comparison.
As seen above, Pentax Q-S1 has a 1.5x Larger sensor area than Fujifilm XP90. 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.