Hi Rudeofus: I have a few starting point suggestions for evaluating the relative granularity of two developers, as I've done a fair bit of this sort of thing.
1. The film should be exposed at the same EI to start
2. I suggest taking the subject matter out of the equation - ie expose a uniform, out of focus test card at various exposure values
3. The films must be developed to the same contrast in both developers
4. Start by evaluating a middle-tone density. Choose matching (or as close as possible) densities from either roll
5. Enlarge the two chosen frames/sheets exactly the same way onto enlarging paper
This is an attempt to evaluate the relative graininess (and characteristics of the grain) of a given type of film, developed in two different developers such that in real life they would both print very similarly in terms of exposure time and contrast. This way you could conclude, for example, that for a given silver density in the negative, intended to produce the same tone in a print (say zone VI), one developer (at a given dilution) produces a grainier or less grainy negative density than another.
I think this is worth considering, as there have been several threads going recently regarding home brew formulas versus XTOL etc, in which people are talking about relative graininess without any sort of methodology.
In your case here, you're comparing a normally developed film in one developer, to a film pushed two stops in a different developer. We can't draw any meaningful conclusions from such a test.
Hope this helps.