Some more thoughts on this topic. If I was just going to shoot relatively static people shots, I would go for the 85 about 90% of the time. It's focal length is more versatile for portraits IMHO. You can get head shots, full body shots, and everything in between by standing within about 15 feet of the subject on a FF. The perspective is right for all of the shots. The 135 on the other hand can do the same, but will require you to stand quite a bit further back, which can be a problem indoors or in tight spots. The perspective is also a bit stronger, but both are natural.
Personally, I will grab the 135 for head shots, outdoor work, events, or anytime people will be moving. I take the 85 for just about every other portrait situation.
If portraits aren't something you do a whole lot, the 70-200 f/2.8IS II is your best choice. It's almost as good as both of these lenses in terms of shallow DOF and bokeh (for most purposes), and as good or better than either one in all aspects other than size and cost.