It depends on what you like/prefer. Looking at some of your flikr page and what you seem to shoot, I could see you with either lens.
Sharpness at 2.8 for my copy of the 135mm is better than the zoom, but my zoom is still really really good. Stopped down there is not much difference. So both are sharp, so to me the benefits of each are below.
135 is a f2.0, black, smaller (much lighter than the zoom). Can have sweet OOF elements at f/2.0.
70-200, is obvious it, has the focal length from 70 through 200. It also has IS. You know the range, you have the f4 non IS. (Over your f4.0 there is the benefit of f2.8 - not an advantage against the 135.
If you had the f4.0 IS my suggestion for you would be easy - go the 135. The extra stop on the 2.8 IS plus the IS could be a winner for you. Depending on how much you use your zoom, this could be a difference for you. Then again 2 stops on the 135 would be nice too.
Both are very nice lenses you will probably like either of them.
(FYI) The zoom is heavy but not bad for me, I use it more than my 135.