Thanks for the report of your tests and the accompanying data.
Just two observations and a question.
The observations. First, the two minute after bath in which the film is soaked in the used developer is not recommended for Pyrocat-HD. This results in useless general stain and for any given time of development reduces negative contrast. Second, differences between developers using the same film are really quite small so comparisons of effective film speed., sharpness, grain and tonal qualities can only be truly meaningful when the comparison negatives are all given the same exposure and developed to the same effective printing contrast.
The question. Why are print exposure times different for the Xtol and Pyrocat-HD negatives (15 seconds) than for the Exactol Lux negative (9 seconds)? If you make three exposures of an identical scene on the same film, and then develop the three films so that each has the same effective printing contrast, each negatives should print with the same exposure time. Print exposure times are based on shadow values at either Zone 1 or Zone II and should not have been different in your tests. The fact that they are different suggests that either negative exposures were not identical or that the negatives were not developed to the same CI.