Philip Bloom put together a great low light comparison of the Panasonic GH5S, Sony a7SII, and Sony a7RIII cameras. Youtube isn’t the best way to judge so he also made the files available via his dropbox here. I have to admit I go back and forth on a few of these shots, but I think I would really like to see this footage pushed a little more.
Panasonic GH5S: B&H Photo / Amazon / Adorama
Sony a7sII: B&H Photo / Amazon / Adorama
Sony a7RIII: B&H Photo / Amazon / Adorama