In my experience the icc way is better if you want to get ‚real‘ colors, the dt chart style approach is better to match camera presets. i never was able to get satisfying results using darktable chart with referencing the cie file …
The dt chart approach requires the use of tonecurve to get proper colors and so it‘s not the best way if used in a filmic workflow (out of the box RAW rendering not up to JPEGs - #67 by MStraeten)