Choosing your portrait lens is not a trivial thing. most good portrait lenses are not cheap, and they will probably serve you for a long time. Preferences may depend on budget, size, focal length, aperture and any other number of factors.
Photographer Manny Ortiz has a quick video up comparing two fo the more Sony popular portrait lenses: The 85mm 1.4 GM and the 70-200mm 2.8 GM. While this is not a pixel peeping kind of review (frankly they are both really nice lenses), it sheds some light on how each one performs and how they feel in the real world.
The first thing that stood up to me, is how far away Manny is from the model (and Manny talks about it at the 5:35 mark)
Manny also mentions that he gets more light into the lens at 1.4, as 1.4 lets two stops of light in compared to the 2.8, and according to Manny the wider aperture also translates to sharper images. Look at the photos and judge for yourself:
Sony GM 85mm 1.4
Sony GM 70-200mm 2.8
[Photoshoot With The New Sony GM 70-200MM 2.8 And 85MM 1.4 | Manny Ortiz]