The 180 would make a pretty nice 'long range' (i.e. outdoor) portrait lens. You'd have to use this lens from some distance............ would give that compressed look which can be flattering depending on the subject.
The 85 would be a more "normal" portrait lens. It works great!
for full length work I use a 50mm mostly and even for headshots I like it even more than the 85 which I found to be too long and the thing did not close focus enough for headshots. But so you know I Have used longer lenses for portraits too , I shot my brother and his new bride with the 400 at f2.8 and it was awesome but hard to communicate to them what I wanted them to do
I use my 50mm f/1.8, 85mm f/1.8 and 180 f/2.8 for portraits constantly. I don't think that you can say which lens is the one you should use, because each does a diffeent job.
You need to know what you want to shoot before you can decide which lens to use.
It is like asking a chef which spices are best--- depends on what you are cooking.
I know I'll end up going out and getting all three of those lenses sooner or later, I think I may start with the 85mm because its the middle of the road between the two, I'll see which end I need more of and that'll be the second of the three I purchase.
