FadedFrontiers A large study is going to be costly and no one is going to be interested in footing the bill. I don’t expect a large scale scientific study, but anyone who has 2 grinders/burrs to compare can take some basing measurements, especially for drip/filter. I do it for every brew I make at home (times, EY, subjective preference score, some flavour perception notes & often a sifting result after dial in).
Gagne’s Q factor seems a lot like the previously used (last 80yrs?) std.dev in sifting. I haven’t been able to find any relationship between a sifted Q factor and overall preference myself, with filter.
This word “geometries” seems very popular at the minute, do you mean shape & size of burrs, or something more detailed (e.g. pre-breaker & finishing area characteristics)?