Although the 120-samples are hard to compare due to the variable contrast between samples, some points are clear to see and just as expected in 4x5: More grain with PO100c, less sharpness and a darker red-patch on the color-chart. Contrast is about equal judged by the white-to-black-patches of the chart which are shown in the picture. Have a look here if you don't know what I'm talking about:

Tonal obviously is not a suitable substitute for APX 100 as Robert already clarified over on the rangefinderforum:

Quote: "The only thing they have in common is they are iso 100."

Robert, thanks for clarifying this!

Now let's go out and expose whatever floats our boats...