News Shooter has an article up summarizing Daniel Peters first impressions with Ursa Mini 4K. Worth a look if you’re considering this camera.
Although not shown in Daniel’s videos it is clear that the URSA Mini 4K version does not come close to the a7S II in low light. It only has 200, 400 and 800 ISO settings and unless you have a very fast aperture lens you will need to light scenes in darker conditions. This is probably the camera’s biggest stumbling block and may be enough to prevent many factual shooters from adopting the camera. We’ll have to wait and see how the sister URSA Mini 4.6K version fares when it finally come out – we still have no date for its release.