Well, I spent a bit of time in the darkroom today and made some quick prints. At first blush, the FP4 seems to have more range, but lower contrast than the Delta 100. Delta 100 seems to have more contrast and 'punch' but is a lot less tolerant of extremes.
I can see how one would vary depending on the effect wanted.
I can see now that I'm going to have to go out and shoot a whole bunch more FP4...Just to see how it works...But honey, I'm conducting photographic experiments