I thought the following test was interesting:
The MX sensor seems to do especially bad in this test.
It's an extreme test (only one candle) but it seems to hold up what I've been suggesting, that all this talk of video being so much better than film in low light for the last 20 years doesn't hold up to much scrutiny. The Alexa and MX are high end large sensor cameras but at 800 ASA neither of them look very usable. The Alexa looks like it might be semi usable with a load of noise reduction at 800ASA. The MX stuff just looks really grim at 800ASA.
This seems to hold closely to my own experiences that all this talk of video being so much infinitely better in low light than film for all these years has been just that. Talk. Usually from people who I suspect had little to no experience with film. It took me a while to realise that all the people telling me my mini dv camera was so much better in low light than film cameras were talking nonsense. (At first I thought I must be missing something because there were so many people saying this stuff) They were usually the same people telling me you didn't need to light anything anymore in fact.
The good news is that the situation seems to be finally changing. The Red Dragon sensor seems very capable in low light and the Sony cameras in the test look hopeful. The Canon 1DC camera is a startling improvement.
I guess if you keep saying something for long enough, maybe it does become true.