D500, your valuable opinion.

You can find my posts in the D500 Event threads to see what I think in more depth of the D500 after handling it at 3 events here in the Seattle area.  Short version, I am thrilled, bordering on ecstatic, annoyed I won't have one until the end of April.

Now, I just sold my 400 f2.8, old 11lb version, for a 600mm VR, same weight, simply cannot afford the new FL versions.  I also have the 300PF and a D810, just sold my D7200, this is for reference.

I think your analysis of the D500/400mm is spot on.  That being said I was just out shooting Short-eared owls with the 600mm plus a 1.7TC on the D7200 and I needed every bit of reach.  As I also have the D810, FX, I now have the advantage of two very good options for using the 300 and 600 interchangeably on the two formats.  Just some more food for thought.

You also mention people, of course the question here is one of lenses.  What focal length do you prefer for people?  Is there an analog to this for DX with Nikon, if not do you mind Sigma or Tokina, both of whom make great DX lenses in the shorter range.

The other big advantage of the D500 vs the D5 is that you can have a lighter and smaller package for travel.

Those are my thoughts, the only reason I would lean to the D5 instead would be if I absolutely needed the extra FPS and the even better low-light performance.  AF will be the same on both, with the exception being that the focus points cover the entire frame on the D500.