70-200 2.8 IS II vs. 85 1.2 II for Portraits?

I own and have used both extensively.

Facts:

1.  Dof, for the same framing is independent of focal length.  a 50 1.2 lens, for the same framing of a head shot, would give you a shallower dof than the 400 f2.8 lens. now, the perspective would obviously be different, and less of background will be included int he 400mm shot, and as such, less clutter, and different bokeh, however, the dof of the 50 1.2 would be less (it would also be less than 200 1.8 lens).

2.  There has been much said about T stop, but shooting them side by side, the 85 1.2@ 1.2 is easily 2 stops faster than the 70-200 2.8.

3. There are other obvious differences.  in favor of 85 1.2, its a 1.2 lens, and smaller and lighter. in the favor of the 70-200, its a zoom hence more versatile, much faster AF, and has IS.

Now, comes personal preferences.  as far as IS goes, I rarely find that I shoot people at faster than 1/100 of sec, due to subject motion blur.  as such, lack of IS, is rarely an issue for me when I am shooting 85.  people able to shoot half or full body shots at f 1.2, in reasonably low light, is extremely useful. I feel that I have more images with the 85 1.2 with the wow factor, at least to me.

however, if I were to keep one, it would be the zoom.

to illustrate, here is a shot at f 1.4, iso 800, 1/200 of second.  a slower shutter speed would have left the image blurred due to her movement. maybe at 1/125 it would have been ok, but not tack shorp (click for full size).