Recs.
Updated
Mentioned price is for a used model.
"The a7R II brings 42MP stills and 4K video to a small, lightweight body. Electronic shutter and in-body image stabilization make for high quality images and video you'll work harder to get, if you get it at all, from comparable DSLRs. BSI-CMOS gives the a7R II class-leading low light performance and respectable dynamic range" according to DP review in 2015.
See: Sony A7 IV vs Sony A7R II Comparison.
See: Panasonic S5 Mark II X vs Sony A7R II Comparison.
SpecsUpdate
Pros
Pro Good 4K video
The camera can capture 4K30 (at up to 100Mbps), 1080p60 and 720p120 video internally and save to XAVC S with S-Log2 color profile. The video is detailed with little noise both in good light and in low light.
It's worth noting that 4K video is slightly better when shooting using the Super 35 region of the sensor instead of the full sensor region while 1080p performs better when shot at full width of the sensor and downsampled.