This will be a short comparison of files from these cameras. Mostly interested in these:
High ISO: The D4 and D3s, along with the Sony a7sII have better performance than the Leica Typ 240. But when it comes to color saturation and separation at lower ISO, the Leica wins. So in some or one system you chose better color over low light performance.
Eelectronic Viewfinder Focusing: Seems that the Sony a7sII has the best EVF from all cameras below $3000. Want to see something better? Look through the $6500 Leica SL. Anyway, the Leica Visoflex (EVF focusing) is doable in bright light and okay in low light when hitting that ISO 6400. The Sony a7sII can see better than your eyes can, so focusing using the built in EVF on the Sony camera is enjoyable, fast, and simply responsive in any kind of bright and low light. Cameras like the D4 or D5 typically see better than your eyes, they are quick and snappy and nail focus almost every single time, even if your eyes can barely see in the dark.
EVF vs OVF: The technology keeps getting much better and EVFs are becoming a joy to use. You see what you get before you take the shor and thats simply amazing. The OVF on the Leica is nice, but at times difficult to nail focus with apertures at f/1.4 and below, try focusing a 90mm Summicron. The OVF in cameras like a D4 or D5 is bright as long as you have lenses with bright apertures, and you typically trust the cameras focusing system. The Sony does not have an OVF and auto focusing tends to be a slow task compared to other cameras.
Can you spot which of these two shots are the Leica M and which is the Sony a7sII?
Answer: Top is the Leica M and bottom is the Sony a7sII. Both RAW files, edited to match in Lightroom, the Sony needed more Vibrance and the Leica needed Color Balance. Both images exported at 10mp. Lens mounted on both cameras was the Leica M Summilux 50mm Aspherical.
The image below, one was super easy to focus manually on the Sony, while on the Leica took me almost two seconds using the EVF and the Nikon D4 was simply point and shoot. The difference here is obvious. Oh, you ask… what ISO? Well, it is ISO 6400: