Both are quite capable. Personally, I think the difference is in the DoF and bokeh. The 50mm f/1.4 is very soft at 1.4 but sharpens up by f/2.0. The problem is that 50mm f/2.0 doesn't squash the background that well at f/2.0, since it's a wider lens.
The 85mm is very sharp right out to f/1.8 AND can kill the background to very pleasant watercolours down to f/2.2 or further and remains perfectly sharp throughout this range.
This is the difference.
My 80-200 f/2.8 (which I use in the 85 focal range) is tack sharp at 2.8 and also has has that "something" that isn't there with the 50mm f/1.4 and it's a full stop and a third slower than the 85 and isn't nearly as sharp...