I did an interesting little thing last night.
I looked at an ABC negative Michael Smith made for me next to a PMK (rollo) negative I made of the same subject, and an Xtol negative I made of a similar subject a few years ago. All were HP5. Differences...
1) The ABC negative is GRAINY. It's like looking at 1600 asa film. BUT, because it is only to be contact printed, the grain doesn't matter. It was also contrastier and held much more detail in highlights and shadows than the other two. Really amazing, except for the grain.
2) The PMK negative...same film, same exposure...was less grainy and appeared to have much less contrast and range, although I think the green stain makes this hard to determine.
3) The XTOL negative was correctly exposed and developed and looked thin compared to the other two. There was a pretty remarkable difference in the areas where negative density would begin to block up compared to the other two. In other words, the PMK and especially the ABC had much more detail holding in much more density, etc.
I have to print these to really see, of course, but I think I will end up concluding that ABC really is best for contact printing, PMK really does hide grain while still outperforming Xtol and will be best for enlarging, and Xtol may be best for someone else.
For what it's worth..