The S1R and the S1 cameras are the world's first to support 4K 60p/50p video recording
Dual I.S. image stabilization - both cameras will have in body image stabilization (as well as some lenses that will also come stabilized the Dual I.S. system and in-lens compensation will work together)
Newly-developed 35 mm full-frame image sensor and image processing engine
Effective pixels: approximately 47M for the S1R and 24M for the S1 (newly developed sensors)
Rugged triaxial tilt LCD: dual hinge LCD – tilt up/down in both orientations
The cameras are weather sealed
Both cameras are based on the L mount which is the same FF mount used by Leica SL cameras.
51.6mm mount diameter
Both will have a top screen and a monitor which flips but also can rotate to the side (but is not fully articulated – sadly).
The cameras are significantly larger than the GH5
There will be 3 initial lenses (at launch) from Panasonic: 24-105mm, 70-200mm (probably with a constant f/4.0 aperture) and a 50mm f/1.4 (Panasonic also promises to have 10 native lenses by 2020 plus quite a few lenses by Leica and possibly some by Sigma).
There will be ten lenses by end of 2020
Image quality, build quality, operability, and performance without compromise
New processing engine
Fast and very accurate autofocus (combination of high-speed contrast detection autofocus and DFD technology)
The AF also includes deep learning Ai
High-precision, high-speed shutter
RAW output video rumored (big question mark here)
The EVF will have higher resolution than that of any existing camera