Dante does not approve; clearly the answer to the question IQ3 100mp Achromatic vs IQ4 150mp (color) is the IQ4 150mp Achromatic
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Jokes aside, DT completed today a 100mp Achromatic vs 100mp Trichromatic (color) comparison that usefully shows the advantages of using a good monochrome camera vs a good color camera: detail, noise, and gradation, artifacts, and the option for infrared capture. You can contact us for raw files.
The increase in detail is modest in most subject matter (though can be significant in specific kinds of subject matter). If I had to stick a number on it I'd estimate 10% for most subject matter and 15-20% for subject matter where the bayer filter is especially problematic. so I suspect an IQ4 150mp will out-resolve an IQ3 100mp Achromatic in almost all real-world situations.
The difference in noise, gradation, and artifacts are independent of resolution so I suspect those advantages would persist. And of course the option for infrared capture is a topic separate from 150mp vs 100mp.
DT has both the backs you reference (IQ3 100mp Achromatic and IQ4 150mp color) and would be glad to assist anyone in the US with any comparisons they wish to make.