I use the 150 for portraits. I can get the camera in far enough distance so as the client is not so nervous.
Also I can have the persons eyes tack sharp whilst the background is a blur.
The 150 is wonderful for head & shoulders and three quarter shots.
For full length portraits and groups I wil usually use the 80mm.
I don't use the 60 mm very much for people photography other than environmental photographs with the people in the scene.
Just what I do.
Hope this helps you.
My wife and I spent a few days here:
Beautiful city and nice people.