I'm in the market for a camera with better high-ISO capability than my current ones. There are more than enough reviews on the internet that measure cameras' high ISO performance. They usually pit one camera against another at particular ISO.
However, I don't think such method is just. It is well known that camera bodies have different "real" ISO sensitivity than their nominal one, and some brands have tendency to inflate the ISO number. So in order to assess the high-ISO performance in real life situation, you need to consider the camera's "effective" ISO, which is also available at some review sites, like DXOMark.
This makes me wonder. Why don't people run high-ISO performance test by using the camera's own auto-ISO mode, with the aperture and shutter speed fixed at the same parameter for each camera? If camera A's ISO is so superb that it only needed 800 in the same available light while others needed 1600, it's not fair to compare camera A's ISO 1600 against other cameras' ISO 1600. You should forget the number and compare at the ISO that was necessary for each camera. This method does depend on the camera's own auto exposure metering, but I think auto exposure meter has less discrepancy between brands than the actual ISO sensitivity. This method will catch two birds with one stone too: you can see which brand tends to jack up the ISO, and you can truly see how the camera does at the given low light situation when the aperture and shutter speed are fixed and the camera is asked to do the best it can with its high ISO.