EL-Nikkor 80mm f/5.6 - 6 elements
EL-Nikkor 75mm f/4 - 4 elements
simple.
I believe a good example of the Fujinon EX should be better than the 80mm Nikkor.
I have the 75 f5.6 Fujinon EP and the 80 f5.6 Nikkor here (and the 75 f4 Nikkor also). Both are outstanding lenses, even at full aperture. The Nikkor has a bit better contrast, but a multicoated Fujinon EX will likely have more contrast than than the EP I have (on loan to me).
My 80 f5.6 Nikkor has a notable amount of dust (or fungus) in it. I haven't been able to get that lens apart for cleaning, but it performed so well that I bought another one NOS a few weeks ago. I was afraid my first one was a fluke, but this one is as good (but no better, the internal dirt seems to make no difference).
As everyone has already stated, the 75 f4 is a fine 4 element lens, but with the bargain prices on great lenses ... My 75 is the older model, but I don't think the newer version is going to change the relative rankings at all.
It is wonderful having such great optics available at the current prices

The flip side is that I need to sell off some of my excess someday, but it is hardly worth the effort.
Mark