Quick unscientific comparison between the Panasonic Lumix S1 at its highest internal movie quality (4k, 422, 10 bit) and the Blackmagic Pocket Cinema Camera BMPCC 4K in Pro-Res & BM Raw.
The Panasonic S1 has the 24-105mm f4 lens - an excellent modern zoom lens. The BMPCC 4K has the Porst 55mm f1.2 at f5.6 without a speedbooster.
The Blackmagic 4K camera is much more fun to use and the menus are simple and clear. The big screen is lovely. Moreover, the image quality looks cinematic and grades well.
The Panasonic S1 is the best value hybrid photography/ videography camera at the time of making this comparison. I had the S1R and sold it. It's a great camera and much better in low light.
But, if I was just interested in making short films, I'd be very tempted by the BMPCC 4K or the BMPCC 6K. The colour is lovely and they're great value.
Of course these tests aren't particularly useful as the lenses are quite different and the grading was done by eye without a colour chart. But as a rough comparison for someone who like black Labrador dogs too, here it is.