Not necessarily the case...
Don't get me wrong here as I love the NX line of cameras. I don't have the NX1, but I do have the NX30, NX300 and NX500 - absolutely love 'em all. However, with the NX300, I won't go above ISO 2000, and with the NX500, I won't go above ISO 3200 when absolutely superb IQ is the end goal. That doesn't mean they can't go higher - by all means no - but what it does mean is that the quality of what you'll get (in very low light) will deteriorate rapidly.
Fuji has always been a leader of sorts with regards to doing higher ISO's fairly well, and their latest X series of cameras have continued that scenario. I wouldn't hesitate (for quality IQ) to use ISO 6400 with the likes of the X series of cameras. Now just to clarify, right now the only X series of camera that I have with 24 MP's is the X-A3. But my other Fuji cameras - the X-E1, X-E2, X-T1, X-M1 and X-A1 all have 16 MP's.
Those comments should in no way be inferred as denigrating the capabilities of the Samsung NX series of cameras. But I must say that among all of my camera brands that I shoot with - that is, the Canon EOS M, Samsung NX, Micro 43 (both Oly and Panny), and Fuji X series - when it comes to covering higher ISO scenarios, the most confidence I have is with the Fuji X cameras.
One other factor - and it can be a big one - regards the covering of skin tones. I love Samsung NX for scenics and architectural photography. But I can't stand Samsung NX for skin tones. If you want absolutely natural, warm skin tones then Fuji is the way to go.
Here's an example or two of skin tones captured by various Fuji X series cameras. Click on the link below each image that says "Original Size" to bring up a larger, clearer version.
Taken with the Fuji X-E1 (16 MP's) using the Fuji EF-42A in bounce mode (with Gary Fong's excellent Lightsphere unit attached to the top of the flash). Shot in AWB, RAW mode, ISO 800, Aperture Priority Mode. Excuse the rear wall color - that was beyond my doing.
Taken with the enthusiast Fuji X30 camera (12 MP's) with the most excellent Meike MK320F flash (TTL dedicated for Fuji) in bounce mode. ISO 100, AWB, RAW mode, Aperture Priority.
Taken with the Fuji X-M1 (16 MP's) at ISO 12,800 - JPG mode, AWB, available light.
Taken with the Fuji X-T1 (16 MP's) - ISO 200, AWB, RAW mode, Aperture Priority, using the very small clip-on SF8A flash that comes with the camera.
I can only comment on cameras I own and use - and I never speculate about gear I've never owned or used.
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Sincerely,
Bernd ("Ben") Herrmann
Fuquay Varina, North Carolina USA