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First, the 135mm field of view is challenging. For portraits, your working distance for all but the tightest shots is a bit far. At f/2, full frame, it isn't easy to get both eyes in focus.
On the other hand, the 135L has that pop factor, really smooth, nice looking transition to the out of focus areas and smooth blurbutter. The 85/1.8 renders more nervous backgrounds. Sigma as well.
The 85L/1.2 v1 is slow, a bit softer, but really pretty for portraits. Maybe $850. An option.