Requirements can be different for different photographers but there are certain aspects of a camera that are important for almost any photographer. Based on those aspects, the best and worse compact system cameras in the market can be decided. Some important technical specs deciding the worth of a camera include its autofocus, its performance under low light, its dynamic range and resolution, and its video and image quality.
With respect to autofocus, Nikon 1 can be considered the best compact system camera option in the market, since it provides great performance when operated under decent light, even though its performance under low light is not very good. The follow-focus characteristics of this camera are better than the most contrast-based systems in the market. On this front, the least efficient camera can be considered the Fujifilm X Pro, particularly when we consider its high price. The optical viewfinder of the camera has the issue of parallax which does not live up to the expectations.
Providing good performance under low light can be considered one of the very best features of the best compact system camera and Fujifilm X Pro delivers fine performance on this front. The low-light ability of the X-Trans sensor build into this camera is hard to beat. Good thing about performance under low light is that it can be mitigated to some extent with the use of a good lens. This is true for earlier Panasonic m4/3 cameras and Olympus OM-D EM5, which otherwise do not do very well under low light.
Good dynamic range can also be considered another important factor in deciding the best compact system camera in the market. On this front, the competition seems to be quite tough and top contenders include Fujifilm X-Pro1, Olympus E-M5 and Sony NEX-7. At the bottom end, we can place Nikon 1, even though the camera does not deliver a very bad performance considering its small sensor.
With respect to resolution, it is once again a bit hard to come up with a single winner. Used with the right lens, NEX-7 can deliver exceptional performance on this front. Fujifilm X-Pro is also close with its only problem that its color resolution sometimes creates trouble. The resolution of Nikon 1 suffers because of its small sensor size but with respect to its own sensor, it delivers good performance.
Now come the two factors that probably play the most important role in the decision made by most photographers, particularly the amateurs. These two features are the video and the image quality. While most of the latest cameras deliver exceptional quality when it comes to video and image, the winner can be decided only with a slight margin. Besides, there are a lot of cameras that give very good video quality but are overheated after doing video for some length of time. When we consider purely with respect to image quality, Olympus cameras and Fujifilm X-Pro seems to be at the top. However, if we consider purely technical aspects, it is almost impossible to pinpoint a single best camera.