To assess which of my two devices is the more accurate I needed a well defined set of colours that I could measure so I bought a CIELAB colour fan:
Here are a typical set of results for the colour in the middle of the screen CIELAB = 75 -20 50:
You can see that the result from the Chinese device on the left is significantly further away (76.18, -13.08, 37.97) than the Canadian Nix device on the right (76, -21, 49). Similar results are seen when measuring random colours across the fan - the Chinese device is never as close as the Nix.
So I will be trusting the Nix from hereon in. The Nix uses a D50 illuminant - this is important to know because it allows comparison of colours independently of light sources.
Just as an initial indication, the first data point: The Hornby Prairie 6110 measures as CIELAB = 24 -6 8 (right tank), or CIELAB = 25 -5 7 (left tank).
More data to follow...