Shifting curves (on 2 sheets of paper and over an illuminator) will show you many things.

1. The shift on the X axis will allow you to read the precise speed difference at mid scale, thus giving you the speed difference in Log E or stops.

2. The shift will show you absolute contrast differences, toe differences and shoulder differences.

When we ran series like this, we plotted each curve on one sheet of paper each. Then we shifted these sheets on a light table to align them in a way that would show the desired characteristic against a norm.

So, for example, Mark has stated that one sample has a softer toe than the other one, but IIRC, the opposite was true. You only see this if you line up the mid scales of those curves.

Try it, you will see what I mean.