Digital BW, The Print

> She said Pan F had finer grain because it was a lower ASA. I said
> that they were different technologies and Delta had tabular grain.
> Her reply was lower ASA = smaller grain. End of story.

I would say rather that is the beginning of the story. 
I'm sure you know grain depends a very much on the contrast to which
the film is developed and the exposure level, and Pan F behaves
differently from Delta in this respect.  If one  "overexposes" films
like delta "for safety" the grain can be worse than similarly
"overexposed" Pan F.  Here I am not implying any particular ISO value
for the films nor exposure technique. 
The choice of developer matters too, and the best results are unlikely
to be achieved with the same developer for both films.  I suspect the
range of variables is easily wide enough so that two photographers,
through differences is technique, can come to the opposite conclusion
about grain, and both be correct.  (Obiously one will have acheived
finer absolute grain, but if they were careful they will have gained
something else from their choice, such a shadow detail or latitude.) 
Ken