Sensor size does matter. That's why most photographers prefer full frame cameras over APS-C and four third cameras. Better dynamic range, lower noise, shallower dof. Also why phones have large camera bumps to accommodate bigger sensors for better quality photos. Software can only do so much.
R9 pro has a lot more useful features for camera enthusiasts, like the ability to attach a magnetic adapter for filters. This phone is really a photographer's camera, no fancy software filters or effects or extreme HDR, just good quality photography features. Somehow it reminds me of the Panasonic Lumix CM1 phone which I used to have also. A camera which has phone features, rather than a phone which has camera features.