I am going to hang a title on you, Tom. The 85mm Guru.
I knew you'd weigh in on this topic as I have seen you on others dealing with the 85mm, and you did not disappoint.
It will probably come down to a deal on either the Sigma or Nikon at the time I have the money together. Most likely I will be looking for used lenses and a lot will depend on the market.
Everything I read so far is favorable for both lenses. So either way I will have a winner. Maybe Santa will carefully take one down the chimney with him for me. (I have tried to be good this year. Tough act to do!)